[InstSimplify] Simplify both operands of select before comparing #121753
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In the simplifySelectWithEquivalence fold, simplify both operands before comparing them, instead of comparing one simplified operand with a non-simplified operand. This is slightly more powerful. These is no impact on compile-time.
llvmbot
added
llvm:instcombine
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@llvm/pr-subscribers-llvm-analysis Author: Nikita Popov (nikic) ChangesIn the simplifySelectWithEquivalence fold, simplify both operands before comparing them, instead of comparing one simplified operand with a non-simplified operand. This is slightly more powerful. These is no impact on compile-time. Full diff: https://github.com/llvm/llvm-project/pull/121753.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8567a0504f54e1..515806428cbb29 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4599,13 +4599,21 @@ static Value *simplifySelectWithEquivalence(Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
- if (simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q.getWithoutUndef(),
+ Value *SimplifiedFalseVal =
+ simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q.getWithoutUndef(),
/* AllowRefinement */ false,
- /* DropFlags */ nullptr, MaxRecurse) == TrueVal)
- return FalseVal;
- if (simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q,
+ /* DropFlags */ nullptr, MaxRecurse);
+ if (!SimplifiedFalseVal)
+ SimplifiedFalseVal = FalseVal;
+
+ Value *SimplifiedTrueVal =
+ simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q,
/* AllowRefinement */ true,
- /* DropFlags */ nullptr, MaxRecurse) == FalseVal)
+ /* DropFlags */ nullptr, MaxRecurse);
+ if (!SimplifiedTrueVal)
+ SimplifiedTrueVal = TrueVal;
+
+ if (SimplifiedFalseVal == SimplifiedTrueVal)
return FalseVal;
return nullptr;
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 0168a804239a89..9de3c2483ba49c 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -4453,11 +4453,8 @@ define i32 @src_no_trans_select_or_eq0_or_and(i32 %x, i32 %y) {
define i32 @src_no_trans_select_or_eq0_or_xor(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_or_eq0_or_xor(
-; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[OR0:%.*]] = icmp eq i32 [[OR]], 0
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X]], [[Y]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR0]], i32 0, i32 [[XOR]]
-; CHECK-NEXT: ret i32 [[COND]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i32 [[XOR]]
;
%or = or i32 %x, %y
%or0 = icmp eq i32 %or, 0
@@ -4492,11 +4489,8 @@ define i32 @src_no_trans_select_or_eq0_xor_or(i32 %x, i32 %y) {
define i32 @src_no_trans_select_and_ne0_xor_or(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_and_ne0_xor_or(
-; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[OR0_NOT:%.*]] = icmp eq i32 [[OR]], 0
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X]], [[Y]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR0_NOT]], i32 0, i32 [[XOR]]
-; CHECK-NEXT: ret i32 [[COND]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i32 [[XOR]]
;
%or = or i32 %x, %y
%or0 = icmp ne i32 %or, 0
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|
@llvm/pr-subscribers-llvm-transforms Author: Nikita Popov (nikic) ChangesIn the simplifySelectWithEquivalence fold, simplify both operands before comparing them, instead of comparing one simplified operand with a non-simplified operand. This is slightly more powerful. These is no impact on compile-time. Full diff: https://github.com/llvm/llvm-project/pull/121753.diff 2 Files Affected:
diff --git a/llvm/lib/Analysis/InstructionSimplify.cpp b/llvm/lib/Analysis/InstructionSimplify.cpp
index 8567a0504f54e1..515806428cbb29 100644
--- a/llvm/lib/Analysis/InstructionSimplify.cpp
+++ b/llvm/lib/Analysis/InstructionSimplify.cpp
@@ -4599,13 +4599,21 @@ static Value *simplifySelectWithEquivalence(Value *CmpLHS, Value *CmpRHS,
Value *TrueVal, Value *FalseVal,
const SimplifyQuery &Q,
unsigned MaxRecurse) {
- if (simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q.getWithoutUndef(),
+ Value *SimplifiedFalseVal =
+ simplifyWithOpReplaced(FalseVal, CmpLHS, CmpRHS, Q.getWithoutUndef(),
/* AllowRefinement */ false,
- /* DropFlags */ nullptr, MaxRecurse) == TrueVal)
- return FalseVal;
- if (simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q,
+ /* DropFlags */ nullptr, MaxRecurse);
+ if (!SimplifiedFalseVal)
+ SimplifiedFalseVal = FalseVal;
+
+ Value *SimplifiedTrueVal =
+ simplifyWithOpReplaced(TrueVal, CmpLHS, CmpRHS, Q,
/* AllowRefinement */ true,
- /* DropFlags */ nullptr, MaxRecurse) == FalseVal)
+ /* DropFlags */ nullptr, MaxRecurse);
+ if (!SimplifiedTrueVal)
+ SimplifiedTrueVal = TrueVal;
+
+ if (SimplifiedFalseVal == SimplifiedTrueVal)
return FalseVal;
return nullptr;
diff --git a/llvm/test/Transforms/InstCombine/select.ll b/llvm/test/Transforms/InstCombine/select.ll
index 0168a804239a89..9de3c2483ba49c 100644
--- a/llvm/test/Transforms/InstCombine/select.ll
+++ b/llvm/test/Transforms/InstCombine/select.ll
@@ -4453,11 +4453,8 @@ define i32 @src_no_trans_select_or_eq0_or_and(i32 %x, i32 %y) {
define i32 @src_no_trans_select_or_eq0_or_xor(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_or_eq0_or_xor(
-; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[OR0:%.*]] = icmp eq i32 [[OR]], 0
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X]], [[Y]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR0]], i32 0, i32 [[XOR]]
-; CHECK-NEXT: ret i32 [[COND]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i32 [[XOR]]
;
%or = or i32 %x, %y
%or0 = icmp eq i32 %or, 0
@@ -4492,11 +4489,8 @@ define i32 @src_no_trans_select_or_eq0_xor_or(i32 %x, i32 %y) {
define i32 @src_no_trans_select_and_ne0_xor_or(i32 %x, i32 %y) {
; CHECK-LABEL: @src_no_trans_select_and_ne0_xor_or(
-; CHECK-NEXT: [[OR:%.*]] = or i32 [[X:%.*]], [[Y:%.*]]
-; CHECK-NEXT: [[OR0_NOT:%.*]] = icmp eq i32 [[OR]], 0
-; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X]], [[Y]]
-; CHECK-NEXT: [[COND:%.*]] = select i1 [[OR0_NOT]], i32 0, i32 [[XOR]]
-; CHECK-NEXT: ret i32 [[COND]]
+; CHECK-NEXT: [[XOR:%.*]] = xor i32 [[X:%.*]], [[Y:%.*]]
+; CHECK-NEXT: ret i32 [[XOR]]
;
%or = or i32 %x, %y
%or0 = icmp ne i32 %or, 0
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nikic
changed the title
paulhuggett
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to paulhuggett/llvm-project
that referenced
this pull request
Jan 7, 2025
…m#121753) In the simplifySelectWithEquivalence fold, simplify both operands before comparing them, instead of comparing one simplified operand with a non-simplified operand. This is slightly more powerful.
nikic
added a commit
to nikic/llvm-project
that referenced
this pull request
Jan 8, 2025
This fold matches complex patterns, for which we have no proof of real-world relevance, and which does not actually handle the originally motivating cases from llvm#71792. In llvm#121708 and llvm#121753 we have handled some simpler variants by extending existing folds. I propose to remove this code until we have evidence that it is useful for something.
nikic
added a commit
that referenced
this pull request
Jan 9, 2025
This fold matches complex patterns, for which we have no proof of real-world relevance, and which does not actually handle the originally motivating cases from #71792 either. In #121708 and #121753 we have handled some simpler variants by extending existing folds. I propose to remove this code until we have evidence that it is useful for something.
github-actions bot
pushed a commit
to arm/arm-toolchain
that referenced
this pull request
Jan 10, 2025
This fold matches complex patterns, for which we have no proof of real-world relevance, and which does not actually handle the originally motivating cases from llvm/llvm-project#71792 either. In llvm/llvm-project#121708 and llvm/llvm-project#121753 we have handled some simpler variants by extending existing folds. I propose to remove this code until we have evidence that it is useful for something.
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In the simplifySelectWithEquivalence fold, simplify both operands before comparing them, instead of comparing one simplified operand with a non-simplified operand. This is slightly more powerful.
There is no impact on compile-time.