[llvm] r324014 - [InstCombine] allow multi-use values in canEvaluate* if all uses are in 1 inst
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Thu Feb 1 13:55:53 PST 2018
Author: spatel
Date: Thu Feb 1 13:55:53 2018
New Revision: 324014
URL: http://llvm.org/viewvc/llvm-project?rev=324014&view=rev
Log:
[InstCombine] allow multi-use values in canEvaluate* if all uses are in 1 inst
This is the enhancement suggested in D42536 to fix a shortcoming in
regular InstCombine's canEvaluate* functionality.
When we have multiple uses of a value, but they're all in one instruction, we can
allow that expression to be narrowed or widened for the same cost as a single-use
value.
AFAICT, this can only matter for multiply: sub/and/or/xor/select would be simplified
away if the operands are the same value; add becomes shl; shifts with a variable shift
amount aren't handled.
Differential Revision: https://reviews.llvm.org/D42739
Modified:
llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll
llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll
Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=324014&r1=324013&r2=324014&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Thu Feb 1 13:55:53 2018
@@ -185,8 +185,14 @@ Value *InstCombiner::EvaluateInDifferent
case Instruction::Shl:
case Instruction::UDiv:
case Instruction::URem: {
- Value *LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
- Value *RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
+ Value *LHS, *RHS;
+ if (I->getOperand(0) == I->getOperand(1)) {
+ // Don't create an unnecessary value if the operands are repeated.
+ LHS = RHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
+ } else {
+ LHS = EvaluateInDifferentType(I->getOperand(0), Ty, isSigned);
+ RHS = EvaluateInDifferentType(I->getOperand(1), Ty, isSigned);
+ }
Res = BinaryOperator::Create((Instruction::BinaryOps)Opc, LHS, RHS);
break;
}
@@ -320,10 +326,12 @@ static bool canNotEvaluateInType(Value *
assert(!isa<Constant>(V) && "Constant should already be handled.");
if (!isa<Instruction>(V))
return true;
- // We can't extend or shrink something that has multiple uses: doing so would
- // require duplicating the instruction in general, which isn't profitable.
+ // We can't extend or shrink something that has multiple uses -- unless those
+ // multiple uses are all in the same instruction -- doing so would require
+ // duplicating the instruction which isn't profitable.
if (!V->hasOneUse())
- return true;
+ if (any_of(V->users(), [&](User *U) { return U != V->user_back(); }))
+ return true;
return false;
}
Modified: llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll?rev=324014&r1=324013&r2=324014&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/cast-mul-select.ll Thu Feb 1 13:55:53 2018
@@ -49,11 +49,9 @@ define i8 @select2(i1 %cond, i8 %x, i8 %
define i32 @eval_trunc_multi_use_in_one_inst(i32 %x) {
; CHECK-LABEL: @eval_trunc_multi_use_in_one_inst(
-; CHECK-NEXT: [[Z:%.*]] = zext i32 [[X:%.*]] to i64
-; CHECK-NEXT: [[A:%.*]] = add nuw nsw i64 [[Z]], 15
-; CHECK-NEXT: [[M:%.*]] = mul i64 [[A]], [[A]]
-; CHECK-NEXT: [[T:%.*]] = trunc i64 [[M]] to i32
-; CHECK-NEXT: ret i32 [[T]]
+; CHECK-NEXT: [[A:%.*]] = add i32 [[X:%.*]], 15
+; CHECK-NEXT: [[M:%.*]] = mul i32 [[A]], [[A]]
+; CHECK-NEXT: ret i32 [[M]]
;
%z = zext i32 %x to i64
%a = add nsw nuw i64 %z, 15
@@ -64,11 +62,9 @@ define i32 @eval_trunc_multi_use_in_one_
define i32 @eval_zext_multi_use_in_one_inst(i32 %x) {
; CHECK-LABEL: @eval_zext_multi_use_in_one_inst(
-; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16
-; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 5
-; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]
-; CHECK-NEXT: [[R:%.*]] = zext i16 [[M]] to i32
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 5
+; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]
+; CHECK-NEXT: ret i32 [[M]]
;
%t = trunc i32 %x to i16
%a = and i16 %t, 5
@@ -79,12 +75,10 @@ define i32 @eval_zext_multi_use_in_one_i
define i32 @eval_sext_multi_use_in_one_inst(i32 %x) {
; CHECK-LABEL: @eval_sext_multi_use_in_one_inst(
-; CHECK-NEXT: [[T:%.*]] = trunc i32 [[X:%.*]] to i16
-; CHECK-NEXT: [[A:%.*]] = and i16 [[T]], 14
-; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i16 [[A]], [[A]]
-; CHECK-NEXT: [[O:%.*]] = or i16 [[M]], -32768
-; CHECK-NEXT: [[R:%.*]] = sext i16 [[O]] to i32
-; CHECK-NEXT: ret i32 [[R]]
+; CHECK-NEXT: [[A:%.*]] = and i32 [[X:%.*]], 14
+; CHECK-NEXT: [[M:%.*]] = mul nuw nsw i32 [[A]], [[A]]
+; CHECK-NEXT: [[O:%.*]] = or i32 [[M]], -32768
+; CHECK-NEXT: ret i32 [[O]]
;
%t = trunc i32 %x to i16
%a = and i16 %t, 14
Modified: llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll?rev=324014&r1=324013&r2=324014&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/icmp-mul-zext.ll Thu Feb 1 13:55:53 2018
@@ -55,13 +55,12 @@ lor.end:
define void @PR33765(i8 %beth) {
; CHECK-LABEL: @PR33765(
-; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i32
+; CHECK-NEXT: [[CONV:%.*]] = zext i8 [[BETH:%.*]] to i16
; CHECK-NEXT: br i1 false, label [[IF_THEN9:%.*]], label [[IF_THEN9]]
; CHECK: if.then9:
-; CHECK-NEXT: [[MUL:%.*]] = mul nuw nsw i32 [[CONV]], [[CONV]]
+; CHECK-NEXT: [[MUL:%.*]] = mul nuw i16 [[CONV]], [[CONV]]
; CHECK-NEXT: [[TINKY:%.*]] = load i16, i16* @glob, align 2
-; CHECK-NEXT: [[TMP1:%.*]] = trunc i32 [[MUL]] to i16
-; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[TMP1]]
+; CHECK-NEXT: [[CONV14:%.*]] = and i16 [[TINKY]], [[MUL]]
; CHECK-NEXT: store i16 [[CONV14]], i16* @glob, align 2
; CHECK-NEXT: ret void
;
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