[llvm] ffc3fb6 - SROA: Enhance speculateSelectInstLoads
Christudasan Devadasan via llvm-commits
llvm-commits at lists.llvm.org
Sat Aug 7 06:10:36 PDT 2021
Author: Christudasan Devadasan
Date: 2021-08-07T09:09:14-04:00
New Revision: ffc3fb665d0a0dccd64cc8c803ad8cc1a0d5dfa1
URL: https://github.com/llvm/llvm-project/commit/ffc3fb665d0a0dccd64cc8c803ad8cc1a0d5dfa1
DIFF: https://github.com/llvm/llvm-project/commit/ffc3fb665d0a0dccd64cc8c803ad8cc1a0d5dfa1.diff
LOG: SROA: Enhance speculateSelectInstLoads
Allow the folding even if there is an
intervening bitcast.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D106667
Added:
llvm/test/Transforms/SROA/select-load.ll
Modified:
llvm/lib/Transforms/Scalar/SROA.cpp
llvm/test/Transforms/SROA/phi-and-select.ll
Removed:
################################################################################
diff --git a/llvm/lib/Transforms/Scalar/SROA.cpp b/llvm/lib/Transforms/Scalar/SROA.cpp
index b3c4308ae80cc..4a6bf97602e52 100644
--- a/llvm/lib/Transforms/Scalar/SROA.cpp
+++ b/llvm/lib/Transforms/Scalar/SROA.cpp
@@ -1330,14 +1330,21 @@ static void speculatePHINodeLoads(PHINode &PN) {
/// %V = select i1 %cond, i32 %V1, i32 %V2
///
/// We can do this to a select if its only uses are loads and if the operand
-/// to the select can be loaded unconditionally.
+/// to the select can be loaded unconditionally. If found an intervening bitcast
+/// with a single use of the load, allow the promotion.
static bool isSafeSelectToSpeculate(SelectInst &SI) {
Value *TValue = SI.getTrueValue();
Value *FValue = SI.getFalseValue();
const DataLayout &DL = SI.getModule()->getDataLayout();
for (User *U : SI.users()) {
- LoadInst *LI = dyn_cast<LoadInst>(U);
+ LoadInst *LI;
+ BitCastInst *BC = dyn_cast<BitCastInst>(U);
+ if (BC && BC->hasOneUse())
+ LI = dyn_cast<LoadInst>(*BC->user_begin());
+ else
+ LI = dyn_cast<LoadInst>(U);
+
if (!LI || !LI->isSimple())
return false;
@@ -1363,10 +1370,24 @@ static void speculateSelectInstLoads(SelectInst &SI) {
Value *FV = SI.getFalseValue();
// Replace the loads of the select with a select of two loads.
while (!SI.use_empty()) {
- LoadInst *LI = cast<LoadInst>(SI.user_back());
+ LoadInst *LI;
+ BitCastInst *BC = dyn_cast<BitCastInst>(SI.user_back());
+ if (BC) {
+ assert(BC->hasOneUse() && "Bitcast should have a single use.");
+ LI = cast<LoadInst>(BC->user_back());
+ } else {
+ LI = cast<LoadInst>(SI.user_back());
+ }
+
assert(LI->isSimple() && "We only speculate simple loads");
IRB.SetInsertPoint(LI);
+ if (BC) {
+ // Cast the operands to bitcast's target type.
+ TV = IRB.CreateBitCast(TV, BC->getType(), TV->getName() + ".sroa.cast");
+ FV = IRB.CreateBitCast(FV, BC->getType(), FV->getName() + ".sroa.cast");
+ }
+
LoadInst *TL = IRB.CreateLoad(LI->getType(), TV,
LI->getName() + ".sroa.speculate.load.true");
LoadInst *FL = IRB.CreateLoad(LI->getType(), FV,
@@ -1390,6 +1411,8 @@ static void speculateSelectInstLoads(SelectInst &SI) {
LLVM_DEBUG(dbgs() << " speculated to: " << *V << "\n");
LI->replaceAllUsesWith(V);
LI->eraseFromParent();
+ if (BC)
+ BC->eraseFromParent();
}
SI.eraseFromParent();
}
diff --git a/llvm/test/Transforms/SROA/phi-and-select.ll b/llvm/test/Transforms/SROA/phi-and-select.ll
index c773714981359..d1863359b1630 100644
--- a/llvm/test/Transforms/SROA/phi-and-select.ll
+++ b/llvm/test/Transforms/SROA/phi-and-select.ll
@@ -60,23 +60,14 @@ entry:
ret i32 %result
}
-; If bitcast isn't considered a safe phi/select use, the alloca
-; remains as an array.
-; FIXME: Why isn't this identical to test2?
define float @test2_bitcast() {
; CHECK-LABEL: @test2_bitcast(
; CHECK-NEXT: entry:
-; CHECK-NEXT: [[A_SROA_0:%.*]] = alloca i32, align 4
-; CHECK-NEXT: [[A_SROA_3:%.*]] = alloca i32, align 4
-; CHECK-NEXT: store i32 0, i32* [[A_SROA_0]], align 4
-; CHECK-NEXT: store i32 1, i32* [[A_SROA_3]], align 4
-; CHECK-NEXT: [[A_SROA_0_0_A_SROA_0_0_V0:%.*]] = load i32, i32* [[A_SROA_0]], align 4
-; CHECK-NEXT: [[A_SROA_3_0_A_SROA_3_4_V1:%.*]] = load i32, i32* [[A_SROA_3]], align 4
-; CHECK-NEXT: [[COND:%.*]] = icmp sle i32 [[A_SROA_0_0_A_SROA_0_0_V0]], [[A_SROA_3_0_A_SROA_3_4_V1]]
-; CHECK-NEXT: [[SELECT:%.*]] = select i1 [[COND]], i32* [[A_SROA_3]], i32* [[A_SROA_0]]
-; CHECK-NEXT: [[SELECT_BC:%.*]] = bitcast i32* [[SELECT]] to float*
-; CHECK-NEXT: [[RESULT:%.*]] = load float, float* [[SELECT_BC]], align 4
-; CHECK-NEXT: ret float [[RESULT]]
+; CHECK-NEXT: [[COND:%.*]] = icmp sle i32 0, 1
+; CHECK-NEXT: [[TMP0:%.*]] = bitcast i32 1 to float
+; CHECK-NEXT: [[TMP1:%.*]] = bitcast i32 0 to float
+; CHECK-NEXT: [[RESULT_SROA_SPECULATED:%.*]] = select i1 [[COND]], float [[TMP0]], float [[TMP1]]
+; CHECK-NEXT: ret float [[RESULT_SROA_SPECULATED]]
;
entry:
%a = alloca [2 x i32]
diff --git a/llvm/test/Transforms/SROA/select-load.ll b/llvm/test/Transforms/SROA/select-load.ll
new file mode 100644
index 0000000000000..60cbae4fb1e59
--- /dev/null
+++ b/llvm/test/Transforms/SROA/select-load.ll
@@ -0,0 +1,35 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -sroa < %s | FileCheck %s
+
+%st.half = type { half }
+
+; Allow speculateSelectInstLoads to fold load and select
+; even if there is an intervening bitcast.
+define <2 x i16> @test_load_bitcast_select(i1 %cond1, i1 %cond2) {
+; CHECK-LABEL: @test_load_bitcast_select(
+; CHECK-NEXT: [[TMP1:%.*]] = bitcast half 0xHFFFF to i16
+; CHECK-NEXT: [[TMP2:%.*]] = bitcast half 0xH0000 to i16
+; CHECK-NEXT: [[LD1_SROA_SPECULATED:%.*]] = select i1 [[COND1:%.*]], i16 [[TMP1]], i16 [[TMP2]]
+; CHECK-NEXT: [[V1:%.*]] = insertelement <2 x i16> undef, i16 [[LD1_SROA_SPECULATED]], i32 0
+; CHECK-NEXT: [[TMP3:%.*]] = bitcast half 0xHFFFF to i16
+; CHECK-NEXT: [[TMP4:%.*]] = bitcast half 0xH0000 to i16
+; CHECK-NEXT: [[LD2_SROA_SPECULATED:%.*]] = select i1 [[COND2:%.*]], i16 [[TMP3]], i16 [[TMP4]]
+; CHECK-NEXT: [[V2:%.*]] = insertelement <2 x i16> [[V1]], i16 [[LD2_SROA_SPECULATED]], i32 1
+; CHECK-NEXT: ret <2 x i16> [[V2]]
+;
+ %true = alloca half, align 2
+ %false = alloca half, align 2
+ store half 0xHFFFF, half* %true, align 2
+ store half 0xH0000, half* %false, align 2
+ %false.cast = bitcast half* %false to %st.half*
+ %true.cast = bitcast half* %true to %st.half*
+ %sel1 = select i1 %cond1, %st.half* %true.cast, %st.half* %false.cast
+ %cast1 = bitcast %st.half* %sel1 to i16*
+ %ld1 = load i16, i16* %cast1, align 2
+ %v1 = insertelement <2 x i16> undef, i16 %ld1, i32 0
+ %sel2 = select i1 %cond2, %st.half* %true.cast, %st.half* %false.cast
+ %cast2 = bitcast %st.half* %sel2 to i16*
+ %ld2 = load i16, i16* %cast2, align 2
+ %v2 = insertelement <2 x i16> %v1, i16 %ld2, i32 1
+ ret <2 x i16> %v2
+}
More information about the llvm-commits
mailing list