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[InstSimplify] Simplify select i1 ConstExpr, i1 true, i1 false to Con…
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…stExpr

`select i1 non-const, i1 true, i1 false` has been optimized to
`non-const`. There is no reason that we can not optimize `select i1
ConstExpr, i1 true, i1 false` to `ConstExpr`.

Reviewed By: nikic

Differential Revision: https://reviews.llvm.org/D151631
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luxufan committed Jun 3, 2023
1 parent 39aa0f5 commit 1ac99bc
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Showing 3 changed files with 28 additions and 18 deletions.
3 changes: 2 additions & 1 deletion llvm/lib/Analysis/InstructionSimplify.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -4640,7 +4640,8 @@ static Value *simplifySelectInst(Value *Cond, Value *TrueVal, Value *FalseVal,
if (auto *CondC = dyn_cast<Constant>(Cond)) {
if (auto *TrueC = dyn_cast<Constant>(TrueVal))
if (auto *FalseC = dyn_cast<Constant>(FalseVal))
return ConstantFoldSelectInstruction(CondC, TrueC, FalseC);
if (Constant *C = ConstantFoldSelectInstruction(CondC, TrueC, FalseC))
return C;

// select poison, X, Y -> poison
if (isa<PoisonValue>(CondC))
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23 changes: 14 additions & 9 deletions llvm/test/Transforms/InstSimplify/select-inseltpoison.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -881,20 +881,27 @@ define <2 x float> @all_constant_false_undef_vec() {
ret <2 x float> %s
}

; Negative tests. Don't fold if the non-undef operand is a constexpr.
@a = external global [3 x ptr]
define i32 @all_constant_false_undef_true_poison_gen_constexpr(i1 %a) {
; CHECK-LABEL: @all_constant_false_undef_true_poison_gen_constexpr(
; CHECK-NEXT: [[S:%.*]] = select i1 [[A:%.*]], i32 ptrtoint (ptr getelementptr inbounds ([3 x ptr], ptr @a, i64 2) to i32), i32 undef
; CHECK-NEXT: ret i32 [[S]]
;
%s = select i1 %a, i32 ptrtoint (ptr getelementptr inbounds ([3 x ptr], ptr @a, i64 2) to i32), i32 undef
ret i32 %s
}

define i32 @all_constant_false_undef_true_constexpr() {
; CHECK-LABEL: @all_constant_false_undef_true_constexpr(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32), i32 undef
; CHECK-NEXT: ret i32 [[S]]
; CHECK-NEXT: ret i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32)
;
%s = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32), i32 undef
ret i32 %s
}

define i32 @all_constant_true_undef_false_constexpr() {
; CHECK-LABEL: @all_constant_true_undef_false_constexpr(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
; CHECK-NEXT: ret i32 [[S]]
; CHECK-NEXT: ret i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
;
%s = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
ret i32 %s
Expand All @@ -903,17 +910,15 @@ define i32 @all_constant_true_undef_false_constexpr() {
; Negative tests. Don't fold if the non-undef operand is a vector containing a constexpr.
define <2 x i32> @all_constant_false_undef_true_constexpr_vec() {
; CHECK-LABEL: @all_constant_false_undef_true_constexpr_vec(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
; CHECK-NEXT: ret <2 x i32> [[S]]
; CHECK-NEXT: ret <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>
;
%s = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
ret <2 x i32> %s
}

define <2 x i32> @all_constant_true_undef_false_constexpr_vec() {
; CHECK-LABEL: @all_constant_true_undef_false_constexpr_vec(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32> <i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
; CHECK-NEXT: ret <2 x i32> [[S]]
; CHECK-NEXT: ret <2 x i32> <i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
;
%s = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32><i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
ret <2 x i32> %s
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20 changes: 12 additions & 8 deletions llvm/test/Transforms/InstSimplify/select.ll
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,14 @@ define i1 @bool_true_or_false(i1 %cond) {
ret i1 %s
}

define i1 @cond_constexpr_bool_true_or_false(i1 %cond) {
; CHECK-LABEL: @cond_constexpr_bool_true_or_false(
; CHECK-NEXT: ret i1 ptrtoint (ptr @cond_constexpr_bool_true_or_false to i1)
;
%s = select i1 ptrtoint (ptr @cond_constexpr_bool_true_or_false to i1), i1 true, i1 false
ret i1 %s
}

define <2 x i1> @bool_true_or_false_vec(<2 x i1> %cond) {
; CHECK-LABEL: @bool_true_or_false_vec(
; CHECK-NEXT: ret <2 x i1> [[COND:%.*]]
Expand Down Expand Up @@ -884,17 +892,15 @@ define <2 x float> @all_constant_false_undef_vec() {
; Negative tests. Don't fold if the non-undef operand is a constexpr.
define i32 @all_constant_false_undef_true_constexpr() {
; CHECK-LABEL: @all_constant_false_undef_true_constexpr(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32), i32 undef
; CHECK-NEXT: ret i32 [[S]]
; CHECK-NEXT: ret i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32)
;
%s = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr to i32), i32 undef
ret i32 %s
}

define i32 @all_constant_true_undef_false_constexpr() {
; CHECK-LABEL: @all_constant_true_undef_false_constexpr(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
; CHECK-NEXT: ret i32 [[S]]
; CHECK-NEXT: ret i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
;
%s = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr to i32)
ret i32 %s
Expand All @@ -903,17 +909,15 @@ define i32 @all_constant_true_undef_false_constexpr() {
; Negative tests. Don't fold if the non-undef operand is a vector containing a constexpr.
define <2 x i32> @all_constant_false_undef_true_constexpr_vec() {
; CHECK-LABEL: @all_constant_false_undef_true_constexpr_vec(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
; CHECK-NEXT: ret <2 x i32> [[S]]
; CHECK-NEXT: ret <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>
;
%s = select i1 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (ptr @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
ret <2 x i32> %s
}

define <2 x i32> @all_constant_true_undef_false_constexpr_vec() {
; CHECK-LABEL: @all_constant_true_undef_false_constexpr_vec(
; CHECK-NEXT: [[S:%.*]] = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32> <i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
; CHECK-NEXT: ret <2 x i32> [[S]]
; CHECK-NEXT: ret <2 x i32> <i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
;
%s = select i1 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32><i32 -1, i32 ptrtoint (ptr @all_constant_true_undef_false_constexpr_vec to i32)>
ret <2 x i32> %s
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