[PATCH] D38263: Gating select arithmetic optimization
Michael Berg via Phabricator via llvm-commits
llvm-commits at lists.llvm.org
Mon Sep 25 14:40:55 PDT 2017
mcberg2017 created this revision.
These changes faciliate positive behavior for arithmetic based select expressions that match its translation criteria, keeping code size gated to neutral or improved scenarios.
https://reviews.llvm.org/D38263
Files:
lib/Transforms/InstCombine/InstructionCombining.cpp
test/Transforms/InstCombine/select_arithmetic.ll
Index: test/Transforms/InstCombine/select_arithmetic.ll
===================================================================
--- test/Transforms/InstCombine/select_arithmetic.ll
+++ test/Transforms/InstCombine/select_arithmetic.ll
@@ -3,17 +3,32 @@
target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
; Tests folding constants from two similar selects that feed a add
-define float @test1(i1 zeroext %arg) #0 {
+define float @test1a(i1 zeroext %arg) #0 {
%tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00
%tmp1 = select i1 %arg, float 1.000000e+00, float 9.000000e+00
%tmp2 = fadd float %tmp, %tmp1
ret float %tmp2
-; CHECK-LABEL: @test1(
+; CHECK-LABEL: @test1a(
; CHECK: %tmp2 = select i1 %arg, float 6.000000e+00, float 1.500000e+01
; CHECK-NOT: fadd
; CHECK: ret float %tmp2
}
+; Tests folding multiple expression constants from similar selects that feed a adds
+define float @test1b(i1 zeroext %arg) #0 {
+ %tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00
+ %tmp1 = select i1 %arg, float 1.000000e+00, float 9.000000e+00
+ %tmp2 = select i1 %arg, float 2.500000e-01, float 4.000000e+00
+ %tmp3 = fadd float %tmp, %tmp1
+ %tmp4 = fadd float %tmp2, %tmp1
+ %tmp5 = fadd float %tmp4, %tmp3
+ ret float %tmp5
+; CHECK-LABEL: @test1b(
+; CHECK: %tmp5 = select i1 %arg, float 7.250000e+00, float 2.800000e+01
+; CHECK-NOT: fadd
+; CHECK: ret float %tmp5
+}
+
; Tests folding constants from two similar selects that feed a sub
define float @test2(i1 zeroext %arg) #0 {
%tmp = select i1 %arg, float 5.000000e+00, float 6.000000e+00
Index: lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- lib/Transforms/InstCombine/InstructionCombining.cpp
+++ lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -731,6 +731,7 @@
Value *SI = nullptr;
if (match(LHS, m_Select(m_Value(A), m_Value(B), m_Value(C))) &&
match(RHS, m_Select(m_Specific(A), m_Value(D), m_Value(E)))) {
+ bool SelectsHaveOneUse = LHS->hasOneUse() && RHS->hasOneUse();
BuilderTy::FastMathFlagGuard Guard(Builder);
if (isa<FPMathOperator>(&I))
Builder.setFastMathFlags(I.getFastMathFlags());
@@ -739,9 +740,9 @@
Value *V2 = SimplifyBinOp(Opcode, B, D, SQ.getWithInstruction(&I));
if (V1 && V2)
SI = Builder.CreateSelect(A, V2, V1);
- else if (V2)
+ else if (V2 && SelectsHaveOneUse)
SI = Builder.CreateSelect(A, V2, Builder.CreateBinOp(Opcode, C, E));
- else if (V1)
+ else if (V1 && SelectsHaveOneUse)
SI = Builder.CreateSelect(A, Builder.CreateBinOp(Opcode, B, D), V1);
if (SI)
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