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merged 4 commits into from
Oct 3, 2025
Merged

[InstCombine] Preserve profile after folding select instructions with conditionals #159666

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383b2f9
[InstCombine] Preserve profile after folding select instructions with…
alanzhao1 Sep 18, 2025
dc8352a
remove unnecessary change
alanzhao1 Sep 18, 2025
9c7a795
forgot to run update_test_checks.py
alanzhao1 Sep 18, 2025
bc68a9d
add the flag for metadata fixes
alanzhao1 Sep 18, 2025
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18 changes: 16 additions & 2 deletions llvm/lib/Transforms/InstCombine/InstCombineSelect.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,7 @@
using namespace llvm;
using namespace PatternMatch;

extern cl::opt<bool> ProfcheckDisableMetadataFixes;

/// Replace a select operand based on an equality comparison with the identity
/// constant of a binop.
Expand Down Expand Up @@ -4521,8 +4522,21 @@ Instruction *InstCombinerImpl::visitSelectInst(SelectInst &SI) {
auto FoldSelectWithAndOrCond = [&](bool IsAnd, Value *A,
Value *B) -> Instruction * {
if (Value *V = simplifySelectInst(B, TrueVal, FalseVal,
SQ.getWithInstruction(&SI)))
return SelectInst::Create(A, IsAnd ? V : TrueVal, IsAnd ? FalseVal : V);
SQ.getWithInstruction(&SI))) {
Value *NewTrueVal = IsAnd ? V : TrueVal;
Value *NewFalseVal = IsAnd ? FalseVal : V;

// If the True and False values don't change, then preserve the branch
// metadata of the original select as the net effect of this change is to
// simplify the conditional.
Instruction *MDFrom = nullptr;
if (NewTrueVal == TrueVal && NewFalseVal == FalseVal &&
!ProfcheckDisableMetadataFixes) {
MDFrom = &SI;
}
return SelectInst::Create(A, NewTrueVal, NewFalseVal, "", nullptr,
MDFrom);
}

// Is (select B, T, F) a SPF?
if (CondVal->hasOneUse() && SelType->isIntOrIntVectorTy()) {
Expand Down
44 changes: 26 additions & 18 deletions llvm/test/Transforms/InstCombine/select-and-cmp.ll
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i32 @select_and_icmp(i32 %x, i32 %y, i32 %z) {
Expand Down Expand Up @@ -114,34 +114,34 @@ define i32 @select_and_icmp_inv(i32 %x, i32 %y, i32 %z) {

; Below used to be negative tests in InstSimplify, but are no more negative cases here

define i32 @select_and_icmp_pred_bad_1(i32 %x, i32 %y, i32 %z) {
define i32 @select_and_icmp_pred_bad_1(i32 %x, i32 %y, i32 %z) !prof !0 {
; CHECK-LABEL: @select_and_icmp_pred_bad_1(
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 [[X:%.*]]
;
%A = icmp eq i32 %x, %z
%B = icmp ne i32 %y, %z
%C = and i1 %A, %B
%D = select i1 %C, i32 %z, i32 %x
%D = select i1 %C, i32 %z, i32 %x, !prof !1
ret i32 %D
}

define i32 @select_and_icmp_pred_bad_2(i32 %x, i32 %y, i32 %z) {
define i32 @select_and_icmp_pred_bad_2(i32 %x, i32 %y, i32 %z) !prof !0 {
; CHECK-LABEL: @select_and_icmp_pred_bad_2(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X:%.*]], !prof [[PROF1:![0-9]+]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
%B = icmp eq i32 %y, %z
%C = and i1 %A, %B
%D = select i1 %C, i32 %z, i32 %x
%D = select i1 %C, i32 %z, i32 %x, !prof !1
ret i32 %D
}

define i32 @select_and_icmp_pred_bad_3(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_pred_bad_3(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X:%.*]], i32 [[Z]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
Expand All @@ -153,8 +153,8 @@ define i32 @select_and_icmp_pred_bad_3(i32 %x, i32 %y, i32 %z) {

define i32 @select_and_icmp_pred_bad_4(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_pred_bad_4(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X:%.*]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
Expand All @@ -166,7 +166,7 @@ define i32 @select_and_icmp_pred_bad_4(i32 %x, i32 %y, i32 %z) {

define i32 @select_and_icmp_alt_bad_1(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_alt_bad_1(
; CHECK-NEXT: ret i32 [[Z]]
; CHECK-NEXT: ret i32 [[Z:%.*]]
;
%A = icmp eq i32 %x, %z
%B = icmp ne i32 %y, %z
Expand All @@ -177,8 +177,8 @@ define i32 @select_and_icmp_alt_bad_1(i32 %x, i32 %y, i32 %z) {

define i32 @select_and_icmp_alt_bad_2(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_alt_bad_2(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X:%.*]], i32 [[Z]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
Expand All @@ -191,8 +191,8 @@ define i32 @select_and_icmp_alt_bad_2(i32 %x, i32 %y, i32 %z) {

define i32 @select_and_icmp_alt_bad_3(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_alt_bad_3(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X:%.*]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
Expand All @@ -204,8 +204,8 @@ define i32 @select_and_icmp_alt_bad_3(i32 %x, i32 %y, i32 %z) {

define i32 @select_and_icmp_alt_bad_4(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_alt_bad_4(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X:%.*]], i32 [[Z]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
Expand Down Expand Up @@ -322,3 +322,11 @@ define i32 @select_and_icmp_alt_bad_false_val(i32 %x, i32 %y, i32 %z, i32 %k) {
%D = select i1 %C, i32 %x, i32 %k
ret i32 %D
}

!0 = !{!"function_entry_count", i64 1000}
!1 = !{!"branch_weights", i32 2, i32 3}

;.
; CHECK: [[META0:![0-9]+]] = !{!"function_entry_count", i64 1000}
; CHECK: [[PROF1]] = !{!"branch_weights", i32 2, i32 3}
;.
50 changes: 29 additions & 21 deletions llvm/test/Transforms/InstCombine/select-or-cmp.ll
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Original file line number Diff line number Diff line change
@@ -1,4 +1,4 @@
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --check-globals
; RUN: opt < %s -passes=instcombine -S | FileCheck %s

define i32 @select_or_icmp(i32 %x, i32 %y, i32 %z) {
Expand Down Expand Up @@ -114,47 +114,47 @@ define i32 @select_or_icmp_inv(i32 %x, i32 %y, i32 %z) {

; Below used to be negative tests in InstSimplify, but are no more negative cases here

define i32 @select_and_icmp_pred_bad_1(i32 %x, i32 %y, i32 %z) {
define i32 @select_and_icmp_pred_bad_1(i32 %x, i32 %y, i32 %z) !prof !0 {
; CHECK-LABEL: @select_and_icmp_pred_bad_1(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X:%.*]], i32 [[Z]], !prof [[PROF1:![0-9]+]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
%B = icmp ne i32 %y, %z
%C = or i1 %A, %B
%D = select i1 %C, i32 %z, i32 %x
%D = select i1 %C, i32 %z, i32 %x, !prof !1
ret i32 %D
}

define i32 @select_and_icmp_pred_bad_2(i32 %x, i32 %y, i32 %z) {
define i32 @select_and_icmp_pred_bad_2(i32 %x, i32 %y, i32 %z) !prof !0 {
; CHECK-LABEL: @select_and_icmp_pred_bad_2(
; CHECK-NEXT: ret i32 [[Z]]
; CHECK-NEXT: ret i32 [[Z:%.*]]
;
%A = icmp ne i32 %x, %z
%B = icmp eq i32 %y, %z
%C = or i1 %A, %B
%D = select i1 %C, i32 %z, i32 %x
%D = select i1 %C, i32 %z, i32 %x, !prof !1
ret i32 %D
}

define i32 @select_and_icmp_pred_bad_3(i32 %x, i32 %y, i32 %z) {
define i32 @select_and_icmp_pred_bad_3(i32 %x, i32 %y, i32 %z) !prof !0 {
; CHECK-LABEL: @select_and_icmp_pred_bad_3(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[Z]], i32 [[X:%.*]], !prof [[PROF2:![0-9]+]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
%B = icmp eq i32 %y, %z
%C = or i1 %A, %B
%D = select i1 %C, i32 %z, i32 %x
%D = select i1 %C, i32 %z, i32 %x, !prof !1
ret i32 %D
}

define i32 @select_and_icmp_pred_bad_4(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_and_icmp_pred_bad_4(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[X:%.*]], i32 [[Z]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
Expand All @@ -166,8 +166,8 @@ define i32 @select_and_icmp_pred_bad_4(i32 %x, i32 %y, i32 %z) {

define i32 @select_or_icmp_alt_bad_1(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_or_icmp_alt_bad_1(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X:%.*]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
Expand All @@ -179,7 +179,7 @@ define i32 @select_or_icmp_alt_bad_1(i32 %x, i32 %y, i32 %z) {

define i32 @select_or_icmp_alt_bad_2(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_or_icmp_alt_bad_2(
; CHECK-NEXT: ret i32 [[X]]
; CHECK-NEXT: ret i32 [[X:%.*]]
;
%A = icmp ne i32 %x, %z
%B = icmp eq i32 %y, %z
Expand All @@ -190,8 +190,8 @@ define i32 @select_or_icmp_alt_bad_2(i32 %x, i32 %y, i32 %z) {

define i32 @select_or_icmp_alt_bad_3(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_or_icmp_alt_bad_3(
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X]], i32 [[Z]]
; CHECK-NEXT: [[B:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B]], i32 [[X:%.*]], i32 [[Z]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp eq i32 %x, %z
Expand All @@ -203,8 +203,8 @@ define i32 @select_or_icmp_alt_bad_3(i32 %x, i32 %y, i32 %z) {

define i32 @select_or_icmp_alt_bad_4(i32 %x, i32 %y, i32 %z) {
; CHECK-LABEL: @select_or_icmp_alt_bad_4(
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X]]
; CHECK-NEXT: [[B_NOT:%.*]] = icmp eq i32 [[Y:%.*]], [[Z:%.*]]
; CHECK-NEXT: [[D:%.*]] = select i1 [[B_NOT]], i32 [[Z]], i32 [[X:%.*]]
; CHECK-NEXT: ret i32 [[D]]
;
%A = icmp ne i32 %x, %z
Expand Down Expand Up @@ -321,3 +321,11 @@ define i32 @select_or_icmp_alt_bad_false_val(i32 %x, i32 %y, i32 %z, i32 %k) {
%D = select i1 %C, i32 %x, i32 %k
ret i32 %D
}

!0 = !{!"function_entry_count", i64 1000}
!1 = !{!"branch_weights", i32 2, i32 3}
;.
; CHECK: [[META0:![0-9]+]] = !{!"function_entry_count", i64 1000}
; CHECK: [[PROF1]] = !{!"branch_weights", i32 3, i32 2}
; CHECK: [[PROF2]] = !{!"branch_weights", i32 2, i32 3}
;.