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[ArgPromotion] Handle pointer arguments of recursive calls (llvm#78735)
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Argument promotion doesn't handle recursive function calls to promote
arguments. This patch adds functionality to handle self recursive
function calls, i.e. whose SCC size is 1. Due to complexity of
ValueTracking in recursive calls with SCC size greater than 1, we bail
out in such cases.
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@vedantparanjape-amd @aaryanshukla
vedantparanjape-amd authored and aaryanshukla committed Jul 14, 2024
1 parent a7fae89 commit 428bed3
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Showing 7 changed files with 525 additions and 5 deletions.
71 changes: 66 additions & 5 deletions llvm/lib/Transforms/IPO/ArgumentPromotion.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -423,9 +423,9 @@ doPromotion(Function *F, FunctionAnalysisManager &FAM,

/// Return true if we can prove that all callees pass in a valid pointer for the
/// specified function argument.
static bool allCallersPassValidPointerForArgument(Argument *Arg,
Align NeededAlign,
uint64_t NeededDerefBytes) {
static bool allCallersPassValidPointerForArgument(
Argument *Arg, SmallPtrSetImpl<CallBase *> &RecursiveCalls,
Align NeededAlign, uint64_t NeededDerefBytes) {
Function *Callee = Arg->getParent();
const DataLayout &DL = Callee->getDataLayout();
APInt Bytes(64, NeededDerefBytes);
Expand All @@ -438,6 +438,33 @@ static bool allCallersPassValidPointerForArgument(Argument *Arg,
// direct callees.
return all_of(Callee->users(), [&](User *U) {
CallBase &CB = cast<CallBase>(*U);
// In case of functions with recursive calls, this check
// (isDereferenceableAndAlignedPointer) will fail when it tries to look at
// the first caller of this function. The caller may or may not have a load,
// incase it doesn't load the pointer being passed, this check will fail.
// So, it's safe to skip the check incase we know that we are dealing with a
// recursive call. For example we have a IR given below.
//
// def fun(ptr %a) {
// ...
// %loadres = load i32, ptr %a, align 4
// %res = call i32 @fun(ptr %a)
// ...
// }
//
// def bar(ptr %x) {
// ...
// %resbar = call i32 @fun(ptr %x)
// ...
// }
//
// Since we record processed recursive calls, we check if the current
// CallBase has been processed before. If yes it means that it is a
// recursive call and we can skip the check just for this call. So, just
// return true.
if (RecursiveCalls.contains(&CB))
return true;

return isDereferenceableAndAlignedPointer(CB.getArgOperand(Arg->getArgNo()),
NeededAlign, Bytes, DL);
});
Expand Down Expand Up @@ -571,6 +598,7 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
SmallVector<const Use *, 16> Worklist;
SmallPtrSet<const Use *, 16> Visited;
SmallVector<LoadInst *, 16> Loads;
SmallPtrSet<CallBase *, 4> RecursiveCalls;
auto AppendUses = [&](const Value *V) {
for (const Use &U : V->uses())
if (Visited.insert(&U).second)
Expand Down Expand Up @@ -611,6 +639,33 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,
// unknown users
}

auto *CB = dyn_cast<CallBase>(V);
Value *PtrArg = cast<Value>(U);
if (CB && PtrArg && CB->getCalledFunction() == CB->getFunction()) {
if (PtrArg != Arg) {
LLVM_DEBUG(dbgs() << "ArgPromotion of " << *Arg << " failed: "
<< "pointer offset is not equal to zero\n");
return false;
}

unsigned int ArgNo = Arg->getArgNo();
if (CB->getArgOperand(ArgNo) != Arg || U->getOperandNo() != ArgNo) {
LLVM_DEBUG(dbgs() << "ArgPromotion of " << *Arg << " failed: "
<< "arg position is different in callee\n");
return false;
}

// We limit promotion to only promoting up to a fixed number of elements
// of the aggregate.
if (MaxElements > 0 && ArgParts.size() > MaxElements) {
LLVM_DEBUG(dbgs() << "ArgPromotion of " << *Arg << " failed: "
<< "more than " << MaxElements << " parts\n");
return false;
}

RecursiveCalls.insert(CB);
continue;
}
// Unknown user.
LLVM_DEBUG(dbgs() << "ArgPromotion of " << *Arg << " failed: "
<< "unknown user " << *V << "\n");
Expand All @@ -619,7 +674,7 @@ static bool findArgParts(Argument *Arg, const DataLayout &DL, AAResults &AAR,

if (NeededDerefBytes || NeededAlign > 1) {
// Try to prove a required deref / aligned requirement.
if (!allCallersPassValidPointerForArgument(Arg, NeededAlign,
if (!allCallersPassValidPointerForArgument(Arg, RecursiveCalls, NeededAlign,
NeededDerefBytes)) {
LLVM_DEBUG(dbgs() << "ArgPromotion of " << *Arg << " failed: "
<< "not dereferenceable or aligned\n");
Expand Down Expand Up @@ -700,6 +755,10 @@ static bool areTypesABICompatible(ArrayRef<Type *> Types, const Function &F,
/// calls the DoPromotion method.
static Function *promoteArguments(Function *F, FunctionAnalysisManager &FAM,
unsigned MaxElements, bool IsRecursive) {
// Due to complexity of handling cases where the SCC has more than one
// component. We want to limit argument promotion of recursive calls to
// just functions that directly call themselves.
bool IsSelfRecursive = false;
// Don't perform argument promotion for naked functions; otherwise we can end
// up removing parameters that are seemingly 'not used' as they are referred
// to in the assembly.
Expand Down Expand Up @@ -745,8 +804,10 @@ static Function *promoteArguments(Function *F, FunctionAnalysisManager &FAM,
if (CB->isMustTailCall())
return nullptr;

if (CB->getFunction() == F)
if (CB->getFunction() == F) {
IsRecursive = true;
IsSelfRecursive = true;
}
}

// Can't change signature of musttail caller
Expand Down
40 changes: 40 additions & 0 deletions llvm/test/Transforms/ArgumentPromotion/recursion/aggregate-promote-recursive.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,40 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
; RUN: opt < %s -passes=argpromotion -S | FileCheck %s

%T = type { i32, i32, i32, i32 }
@G = constant %T { i32 0, i32 0, i32 17, i32 25 }

define internal i32 @test(ptr %p) {
; CHECK-LABEL: define {{[^@]+}}@test
; CHECK-SAME: (i32 [[P_8_VAL:%.*]], i32 [[P_12_VAL:%.*]]) {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[V:%.*]] = add i32 [[P_12_VAL]], [[P_8_VAL]]
; CHECK-NEXT: [[RET:%.*]] = call i32 @test(i32 [[P_8_VAL]], i32 [[P_12_VAL]])
; CHECK-NEXT: [[ARET:%.*]] = add i32 [[V]], [[RET]]
; CHECK-NEXT: ret i32 [[ARET]]
;
entry:
%a.gep = getelementptr %T, ptr %p, i64 0, i32 3
%b.gep = getelementptr %T, ptr %p, i64 0, i32 2
%a = load i32, ptr %a.gep
%b = load i32, ptr %b.gep
%v = add i32 %a, %b
%ret = call i32 @test(ptr %p)
%aret = add i32 %v, %ret
ret i32 %aret
}

define i32 @caller() {
; CHECK-LABEL: define {{[^@]+}}@caller() {
; CHECK-NEXT: entry:
; CHECK-NEXT: [[TMP0:%.*]] = getelementptr i8, ptr @G, i64 8
; CHECK-NEXT: [[G_VAL:%.*]] = load i32, ptr [[TMP0]], align 4
; CHECK-NEXT: [[TMP1:%.*]] = getelementptr i8, ptr @G, i64 12
; CHECK-NEXT: [[G_VAL1:%.*]] = load i32, ptr [[TMP1]], align 4
; CHECK-NEXT: [[V:%.*]] = call i32 @test(i32 [[G_VAL]], i32 [[G_VAL1]])
; CHECK-NEXT: ret i32 [[V]]
;
entry:
%v = call i32 @test(ptr @G)
ret i32 %v
}
65 changes: 65 additions & 0 deletions llvm/test/Transforms/ArgumentPromotion/recursion/argpromotion-recursion-pr1259.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,65 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=argpromotion < %s | FileCheck %s
define internal i32 @foo(ptr %x, i32 %n, i32 %m) {
; CHECK-LABEL: define internal i32 @foo(
; CHECK-SAME: i32 [[X_0_VAL:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[N]], 0
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[SUBVAL:%.*]] = sub i32 [[N]], 1
; CHECK-NEXT: [[CALLRET:%.*]] = call i32 @foo(i32 [[X_0_VAL]], i32 [[SUBVAL]], i32 [[X_0_VAL]])
; CHECK-NEXT: [[SUBVAL2:%.*]] = sub i32 [[N]], 2
; CHECK-NEXT: [[CALLRET2:%.*]] = call i32 @foo(i32 [[X_0_VAL]], i32 [[SUBVAL2]], i32 [[M]])
; CHECK-NEXT: [[CMP2:%.*]] = add i32 [[CALLRET]], [[CALLRET2]]
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[COND_NEXT:.*]]:
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[X_0_VAL]], %[[COND_TRUE]] ], [ [[CMP2]], %[[COND_FALSE]] ], [ poison, %[[COND_NEXT]] ]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry:
%cmp = icmp ne i32 %n, 0
br i1 %cmp, label %cond_true, label %cond_false

cond_true: ; preds = %entry
%val = load i32, ptr %x, align 4
br label %return

cond_false: ; preds = %entry
%val2 = load i32, ptr %x, align 4
%subval = sub i32 %n, 1
%callret = call i32 @foo(ptr %x, i32 %subval, i32 %val2)
%subval2 = sub i32 %n, 2
%callret2 = call i32 @foo(ptr %x, i32 %subval2, i32 %m)
%cmp2 = add i32 %callret, %callret2
br label %return

cond_next: ; No predecessors!
br label %return

return: ; preds = %cond_next, %cond_false, %cond_true
%retval.0 = phi i32 [ %val, %cond_true ], [ %cmp2, %cond_false ], [ poison, %cond_next ]
ret i32 %retval.0
}

define i32 @bar(ptr align(4) dereferenceable(4) %x, i32 %n, i32 %m) {
; CHECK-LABEL: define i32 @bar(
; CHECK-SAME: ptr align 4 dereferenceable(4) [[X:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[X_VAL:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: [[CALLRET3:%.*]] = call i32 @foo(i32 [[X_VAL]], i32 [[N]], i32 [[M]])
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: ret i32 [[CALLRET3]]
;
entry:
%callret3 = call i32 @foo(ptr %x, i32 %n, i32 %m)
br label %return

return: ; preds = %entry
ret i32 %callret3
}
68 changes: 68 additions & 0 deletions llvm/test/Transforms/ArgumentPromotion/recursion/recursion-arg-position-pr1259.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,68 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=argpromotion < %s | FileCheck %s
define internal i32 @foo(ptr %x, ptr %y, i32 %n, i32 %m) {
; CHECK-LABEL: define internal i32 @foo(
; CHECK-SAME: ptr [[X:%.*]], ptr [[Y:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[N]], 0
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[VAL:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[VAL2:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: [[VAL3:%.*]] = load i32, ptr [[Y]], align 4
; CHECK-NEXT: [[SUBVAL:%.*]] = sub i32 [[N]], [[VAL3]]
; CHECK-NEXT: [[CALLRET:%.*]] = call i32 @foo(ptr [[X]], ptr [[Y]], i32 [[SUBVAL]], i32 [[VAL2]])
; CHECK-NEXT: [[SUBVAL2:%.*]] = sub i32 [[N]], 2
; CHECK-NEXT: [[CALLRET2:%.*]] = call i32 @foo(ptr [[Y]], ptr [[X]], i32 [[SUBVAL2]], i32 [[M]])
; CHECK-NEXT: [[CMP2:%.*]] = add i32 [[CALLRET]], [[CALLRET2]]
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[COND_NEXT:.*]]:
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[VAL]], %[[COND_TRUE]] ], [ [[CMP2]], %[[COND_FALSE]] ], [ poison, %[[COND_NEXT]] ]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry:
%cmp = icmp ne i32 %n, 0
br i1 %cmp, label %cond_true, label %cond_false

cond_true: ; preds = %entry
%val = load i32, ptr %x, align 4
br label %return

cond_false: ; preds = %entry
%val2 = load i32, ptr %x, align 4
%val3 = load i32, ptr %y, align 4
%subval = sub i32 %n, %val3
%callret = call i32 @foo(ptr %x, ptr %y, i32 %subval, i32 %val2)
%subval2 = sub i32 %n, 2
%callret2 = call i32 @foo(ptr %y, ptr %x, i32 %subval2, i32 %m)
%cmp2 = add i32 %callret, %callret2
br label %return

cond_next: ; No predecessors!
br label %return

return: ; preds = %cond_next, %cond_false, %cond_true
%retval.0 = phi i32 [ %val, %cond_true ], [ %cmp2, %cond_false ], [ poison, %cond_next ]
ret i32 %retval.0
}

define i32 @bar(ptr align(4) dereferenceable(4) %x, ptr align(4) dereferenceable(4) %y, i32 %n, i32 %m) {
; CHECK-LABEL: define i32 @bar(
; CHECK-SAME: ptr align 4 dereferenceable(4) [[X:%.*]], ptr align 4 dereferenceable(4) [[Y:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CALLRET3:%.*]] = call i32 @foo(ptr [[X]], ptr [[Y]], i32 [[N]], i32 [[M]])
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: ret i32 [[CALLRET3]]
;
entry:
%callret3 = call i32 @foo(ptr %x, ptr %y, i32 %n, i32 %m)
br label %return

return: ; preds = %entry
ret i32 %callret3
}
84 changes: 84 additions & 0 deletions llvm/test/Transforms/ArgumentPromotion/recursion/recursion-mixed-calls.ll
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Original file line number Diff line number Diff line change
@@ -0,0 +1,84 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
; RUN: opt -S -passes=argpromotion < %s | FileCheck %s
define internal i32 @zoo(ptr %x, i32 %m) {
; CHECK-LABEL: define internal i32 @zoo(
; CHECK-SAME: i32 [[X_0_VAL:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[RESZOO:%.*]] = add i32 [[X_0_VAL]], [[M]]
; CHECK-NEXT: ret i32 [[X_0_VAL]]
;
%valzoo = load i32, ptr %x, align 4
%reszoo = add i32 %valzoo, %m
ret i32 %valzoo
}

define internal i32 @foo(ptr %x, ptr %y, i32 %n, i32 %m) {
; CHECK-LABEL: define internal i32 @foo(
; CHECK-SAME: ptr [[X:%.*]], i32 [[Y_0_VAL:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[CMP:%.*]] = icmp ne i32 [[N]], 0
; CHECK-NEXT: br i1 [[CMP]], label %[[COND_TRUE:.*]], label %[[COND_FALSE:.*]]
; CHECK: [[COND_TRUE]]:
; CHECK-NEXT: [[VAL:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[COND_FALSE]]:
; CHECK-NEXT: [[VAL2:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: [[SUBVAL:%.*]] = sub i32 [[N]], [[Y_0_VAL]]
; CHECK-NEXT: [[CALLRET:%.*]] = call i32 @foo(ptr [[X]], i32 [[Y_0_VAL]], i32 [[SUBVAL]], i32 [[VAL2]])
; CHECK-NEXT: [[SUBVAL2:%.*]] = sub i32 [[N]], 2
; CHECK-NEXT: [[CALLRET2:%.*]] = call i32 @foo(ptr [[X]], i32 [[Y_0_VAL]], i32 [[SUBVAL2]], i32 [[M]])
; CHECK-NEXT: [[CMP1:%.*]] = add i32 [[CALLRET]], [[CALLRET2]]
; CHECK-NEXT: [[X_VAL:%.*]] = load i32, ptr [[X]], align 4
; CHECK-NEXT: [[CALLRETFINAL:%.*]] = call i32 @zoo(i32 [[X_VAL]], i32 [[M]])
; CHECK-NEXT: [[CMP2:%.*]] = add i32 [[CMP1]], [[CALLRETFINAL]]
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[COND_NEXT:.*]]:
; CHECK-NEXT: br label %[[RETURN]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: [[RETVAL_0:%.*]] = phi i32 [ [[VAL]], %[[COND_TRUE]] ], [ [[CMP2]], %[[COND_FALSE]] ], [ poison, %[[COND_NEXT]] ]
; CHECK-NEXT: ret i32 [[RETVAL_0]]
;
entry:
%cmp = icmp ne i32 %n, 0
br i1 %cmp, label %cond_true, label %cond_false

cond_true: ; preds = %entry
%val = load i32, ptr %x, align 4
br label %return

cond_false: ; preds = %entry
%val2 = load i32, ptr %x, align 4
%val3 = load i32, ptr %y, align 4
%subval = sub i32 %n, %val3
%callret = call i32 @foo(ptr %x, ptr %y, i32 %subval, i32 %val2)
%subval2 = sub i32 %n, 2
%callret2 = call i32 @foo(ptr %x, ptr %y, i32 %subval2, i32 %m)
%cmp1 = add i32 %callret, %callret2
%callretfinal = call i32 @zoo(ptr %x, i32 %m)
%cmp2 = add i32 %cmp1, %callretfinal
br label %return

cond_next: ; No predecessors!
br label %return

return: ; preds = %cond_next, %cond_false, %cond_true
%retval.0 = phi i32 [ %val, %cond_true ], [ %cmp2, %cond_false ], [ poison, %cond_next ]
ret i32 %retval.0
}

define i32 @bar(ptr align(4) dereferenceable(4) %x, ptr align(4) dereferenceable(4) %y, i32 %n, i32 %m) {
; CHECK-LABEL: define i32 @bar(
; CHECK-SAME: ptr align 4 dereferenceable(4) [[X:%.*]], ptr align 4 dereferenceable(4) [[Y:%.*]], i32 [[N:%.*]], i32 [[M:%.*]]) {
; CHECK-NEXT: [[ENTRY:.*:]]
; CHECK-NEXT: [[Y_VAL:%.*]] = load i32, ptr [[Y]], align 4
; CHECK-NEXT: [[CALLRET3:%.*]] = call i32 @foo(ptr [[X]], i32 [[Y_VAL]], i32 [[N]], i32 [[M]])
; CHECK-NEXT: br label %[[RETURN:.*]]
; CHECK: [[RETURN]]:
; CHECK-NEXT: ret i32 [[CALLRET3]]
;
entry:
%callret3 = call i32 @foo(ptr %x, ptr %y, i32 %n, i32 %m)
br label %return

return: ; preds = %entry
ret i32 %callret3
}
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