[llvm] cd9a52b - [AArch64][GlobalISel] Fold binops on the true side of G_SELECT
Jessica Paquette via llvm-commits
llvm-commits at lists.llvm.org
Tue Dec 8 10:43:36 PST 2020
Author: Jessica Paquette
Date: 2020-12-08T10:42:59-08:00
New Revision: cd9a52b99e685e8a77dd85d25c7d1ec8b86b9f55
URL: https://github.com/llvm/llvm-project/commit/cd9a52b99e685e8a77dd85d25c7d1ec8b86b9f55
DIFF: https://github.com/llvm/llvm-project/commit/cd9a52b99e685e8a77dd85d25c7d1ec8b86b9f55.diff
LOG: [AArch64][GlobalISel] Fold binops on the true side of G_SELECT
This implements the following folds:
```
G_SELECT cc, (G_SUB 0, %x), %false -> CSNEG %x, %false, inv_cc
G_SELECT cc, (G_XOR x, -1), %false -> CSINV %x, %false, inv_cc
```
This is similar to the folds introduced in
5bc0bd05e6a8d788e08cdf3d154f3a33202aee53.
In 5bc0bd05e6a8d788e08cdf3d154f3a33202aee53 I mentioned that we may prefer to do
this in AArch64PostLegalizerLowering.
I think that it's probably better to do this in the selector. The way we select
G_SELECT depends on what register banks end up being assigned to it. If we did
this in AArch64PostLegalizerLowering, then we'd end up checking *every* G_SELECT
to see if it's worth swapping operands. Doing it in the selector allows us to
restrict the optimization to only relevant G_SELECTs.
Also fix up some comments in `TryFoldBinOpIntoSelect` which are kind of
confusing IMO.
Example IR: https://godbolt.org/z/3qPGca
Differential Revision: https://reviews.llvm.org/D92860
Added:
Modified:
llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir
Removed:
################################################################################
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
index 493167e284cf..c447f75681e7 100644
--- a/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
+++ b/llvm/lib/Target/AArch64/GISel/AArch64InstructionSelector.cpp
@@ -1033,31 +1033,36 @@ AArch64InstructionSelector::emitSelect(Register Dst, Register True,
// By default, we'll try and emit a CSEL.
unsigned Opc = Is32Bit ? AArch64::CSELWr : AArch64::CSELXr;
bool Optimized = false;
- auto TryFoldBinOpIntoSelect = [&Opc, &False, Is32Bit, &MRI]() {
+ auto TryFoldBinOpIntoSelect = [&Opc, Is32Bit, &CC, &MRI](Register &Reg,
+ bool Invert) {
// Attempt to fold:
//
- // sub = G_SUB 0, x
- // select = G_SELECT cc, true, sub
+ // %sub = G_SUB 0, %x
+ // %select = G_SELECT cc, %reg, %sub
//
// Into:
- // select = CSNEG true, x, cc
+ // %select = CSNEG %reg, %x, cc
Register MatchReg;
- if (mi_match(False, MRI, m_Neg(m_Reg(MatchReg)))) {
+ if (mi_match(Reg, MRI, m_Neg(m_Reg(MatchReg)))) {
Opc = Is32Bit ? AArch64::CSNEGWr : AArch64::CSNEGXr;
- False = MatchReg;
+ Reg = MatchReg;
+ if (Invert)
+ CC = AArch64CC::getInvertedCondCode(CC);
return true;
}
// Attempt to fold:
//
- // xor = G_XOR x, -1
- // select = G_SELECT cc, true, xor
+ // %xor = G_XOR %x, -1
+ // %select = G_SELECT cc, %reg, %xor
//
// Into:
- // select = CSINV true, x, cc
- if (mi_match(False, MRI, m_Not(m_Reg(MatchReg)))) {
+ // %select = CSINV %reg, %x, cc
+ if (mi_match(Reg, MRI, m_Not(m_Reg(MatchReg)))) {
Opc = Is32Bit ? AArch64::CSINVWr : AArch64::CSINVXr;
- False = MatchReg;
+ Reg = MatchReg;
+ if (Invert)
+ CC = AArch64CC::getInvertedCondCode(CC);
return true;
}
@@ -1139,7 +1144,8 @@ AArch64InstructionSelector::emitSelect(Register Dst, Register True,
return false;
};
- Optimized |= TryFoldBinOpIntoSelect();
+ Optimized |= TryFoldBinOpIntoSelect(False, /*Invert = */ false);
+ Optimized |= TryFoldBinOpIntoSelect(True, /*Invert = */ true);
Optimized |= TryOptSelectCst();
auto SelectInst = MIB.buildInstr(Opc, {Dst}, {True, False}).addImm(CC);
constrainSelectedInstRegOperands(*SelectInst, TII, TRI, RBI);
diff --git a/llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir b/llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir
index 2d7928f906ed..d2eee15c5cb6 100644
--- a/llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir
+++ b/llvm/test/CodeGen/AArch64/GlobalISel/select-select.mir
@@ -376,6 +376,36 @@ body: |
$w0 = COPY %select(s32)
RET_ReallyLR implicit $w0
+...
+---
+name: csneg_inverted_cc
+legalized: true
+regBankSelected: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $w0, $w1, $w2
+ ; G_SELECT cc, (G_SUB 0, %x), %false -> CSNEG %x, %false, inv_cc
+
+ ; CHECK-LABEL: name: csneg_inverted_cc
+ ; CHECK: liveins: $w0, $w1, $w2
+ ; CHECK: %reg0:gpr32 = COPY $w0
+ ; CHECK: %reg1:gpr32 = COPY $w1
+ ; CHECK: %f:gpr32 = COPY $w2
+ ; CHECK: [[ANDSWri:%[0-9]+]]:gpr32 = ANDSWri %reg0, 0, implicit-def $nzcv
+ ; CHECK: %select:gpr32 = CSNEGWr %reg1, %f, 0, implicit $nzcv
+ ; CHECK: $w0 = COPY %select
+ ; CHECK: RET_ReallyLR implicit $w0
+ %reg0:gpr(s32) = COPY $w0
+ %cond:gpr(s1) = G_TRUNC %reg0(s32)
+ %reg1:gpr(s32) = COPY $w1
+ %f:gpr(s32) = COPY $w2
+ %zero:gpr(s32) = G_CONSTANT i32 0
+ %sub:gpr(s32) = G_SUB %zero(s32), %reg1
+ %select:gpr(s32) = G_SELECT %cond(s1), %sub, %f
+ $w0 = COPY %select(s32)
+ RET_ReallyLR implicit $w0
+
...
---
name: csneg_s64
@@ -467,6 +497,36 @@ body: |
$w0 = COPY %select(s32)
RET_ReallyLR implicit $w0
+...
+---
+name: csinv_inverted_cc
+legalized: true
+regBankSelected: true
+tracksRegLiveness: true
+body: |
+ bb.0:
+ liveins: $w0, $w1, $w2
+ ; G_SELECT cc, (G_XOR x, -1), %false -> CSINV %x, %false, inv_cc
+
+ ; CHECK-LABEL: name: csinv_inverted_cc
+ ; CHECK: liveins: $w0, $w1, $w2
+ ; CHECK: %reg0:gpr32 = COPY $w0
+ ; CHECK: %reg1:gpr32 = COPY $w1
+ ; CHECK: %f:gpr32 = COPY $w2
+ ; CHECK: [[ANDSWri:%[0-9]+]]:gpr32 = ANDSWri %reg0, 0, implicit-def $nzcv
+ ; CHECK: %select:gpr32 = CSINVWr %reg1, %f, 0, implicit $nzcv
+ ; CHECK: $w0 = COPY %select
+ ; CHECK: RET_ReallyLR implicit $w0
+ %reg0:gpr(s32) = COPY $w0
+ %reg1:gpr(s32) = COPY $w1
+ %cond:gpr(s1) = G_TRUNC %reg0(s32)
+ %f:gpr(s32) = COPY $w2
+ %negative_one:gpr(s32) = G_CONSTANT i32 -1
+ %xor:gpr(s32) = G_XOR %reg1(s32), %negative_one
+ %select:gpr(s32) = G_SELECT %cond(s1), %xor, %f
+ $w0 = COPY %select(s32)
+ RET_ReallyLR implicit $w0
+
...
---
name: csinv_s64
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