[llvm] r343100 - [PowerPC] optimize conditional branch on CRSET/CRUNSET
Hiroshi Inoue via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 26 05:32:45 PDT 2018
Author: inouehrs
Date: Wed Sep 26 05:32:45 2018
New Revision: 343100
URL: http://llvm.org/viewvc/llvm-project?rev=343100&view=rev
Log:
[PowerPC] optimize conditional branch on CRSET/CRUNSET
This patch adds a check to optimize conditional branch (BC and BCn) based on a constant set by CRSET or CRUNSET.
Other optimizers, such as block placement, may generate such code and hence
I do this at the very end of the optimization in pre-emit peephole pass.
A conditional branch based on a constant is eliminated or converted into unconditional branch.
Also CRSET/CRUNSET is eliminated if the condition code register is not used
by instruction other than the branch to be optimized.
Differential Revision: https://reviews.llvm.org/D52345
Added:
llvm/trunk/test/CodeGen/PowerPC/setcr_bc.mir
llvm/trunk/test/CodeGen/PowerPC/setcr_bc2.mir
Modified:
llvm/trunk/lib/Target/PowerPC/PPCPreEmitPeephole.cpp
Modified: llvm/trunk/lib/Target/PowerPC/PPCPreEmitPeephole.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCPreEmitPeephole.cpp?rev=343100&r1=343099&r2=343100&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCPreEmitPeephole.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCPreEmitPeephole.cpp Wed Sep 26 05:32:45 2018
@@ -18,6 +18,7 @@
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/LivePhysRegs.h"
+#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
@@ -60,6 +61,7 @@ namespace {
return false;
bool Changed = false;
const PPCInstrInfo *TII = MF.getSubtarget<PPCSubtarget>().getInstrInfo();
+ const TargetRegisterInfo *TRI = MF.getSubtarget().getRegisterInfo();
SmallVector<MachineInstr *, 4> InstrsToErase;
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
@@ -74,6 +76,75 @@ namespace {
}
}
}
+
+ // Eliminate conditional branch based on a constant CR bit by
+ // CRSET or CRUNSET. We eliminate the conditional branch or
+ // convert it into an unconditional branch. Also, if the CR bit
+ // is not used by other instructions, we eliminate CRSET as well.
+ auto I = MBB.getFirstInstrTerminator();
+ if (I == MBB.instr_end())
+ continue;
+ MachineInstr *Br = &*I;
+ if (Br->getOpcode() != PPC::BC && Br->getOpcode() != PPC::BCn)
+ continue;
+ MachineInstr *CRSetMI = nullptr;
+ unsigned CRBit = Br->getOperand(0).getReg();
+ unsigned CRReg = getCRFromCRBit(CRBit);
+ bool SeenUse = false;
+ MachineBasicBlock::reverse_iterator It = Br, Er = MBB.rend();
+ for (It++; It != Er; It++) {
+ if (It->modifiesRegister(CRBit, TRI)) {
+ if ((It->getOpcode() == PPC::CRUNSET ||
+ It->getOpcode() == PPC::CRSET) &&
+ It->getOperand(0).getReg() == CRBit)
+ CRSetMI = &*It;
+ break;
+ }
+ if (It->readsRegister(CRBit, TRI))
+ SeenUse = true;
+ }
+ if (!CRSetMI) continue;
+
+ unsigned CRSetOp = CRSetMI->getOpcode();
+ if ((Br->getOpcode() == PPC::BCn && CRSetOp == PPC::CRSET) ||
+ (Br->getOpcode() == PPC::BC && CRSetOp == PPC::CRUNSET)) {
+ // Remove this branch since it cannot be taken.
+ InstrsToErase.push_back(Br);
+ MBB.removeSuccessor(Br->getOperand(1).getMBB());
+ }
+ else {
+ // This conditional branch is always taken. So, remove all branches
+ // and insert an unconditional branch to the destination of this.
+ MachineBasicBlock::iterator It = Br, Er = MBB.end();
+ for (; It != Er && !SeenUse; It++) {
+ if (It->isDebugInstr()) continue;
+ assert(It->isTerminator() && "Non-terminator after a terminator");
+ InstrsToErase.push_back(&*It);
+ }
+ if (!MBB.isLayoutSuccessor(Br->getOperand(1).getMBB())) {
+ ArrayRef<MachineOperand> NoCond;
+ TII->insertBranch(MBB, Br->getOperand(1).getMBB(), nullptr,
+ NoCond, Br->getDebugLoc());
+ }
+ for (auto &Succ : MBB.successors())
+ if (Succ != Br->getOperand(1).getMBB()) {
+ MBB.removeSuccessor(Succ);
+ break;
+ }
+ }
+
+ // If the CRBit is not used by another instruction, we can eliminate
+ // CRSET/CRUNSET instruction.
+ if (!SeenUse) {
+ // We need to check use of the CRBit in successors.
+ for (auto &SuccMBB : MBB.successors())
+ if (SuccMBB->isLiveIn(CRBit) || SuccMBB->isLiveIn(CRReg)) {
+ SeenUse = true;
+ break;
+ }
+ if (!SeenUse)
+ InstrsToErase.push_back(CRSetMI);
+ }
}
for (MachineInstr *MI : InstrsToErase) {
LLVM_DEBUG(dbgs() << "PPC pre-emit peephole: erasing instruction: ");
Added: llvm/trunk/test/CodeGen/PowerPC/setcr_bc.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/setcr_bc.mir?rev=343100&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/setcr_bc.mir (added)
+++ llvm/trunk/test/CodeGen/PowerPC/setcr_bc.mir Wed Sep 26 05:32:45 2018
@@ -0,0 +1,132 @@
+# RUN: llc -verify-machineinstrs -start-before=ppc-pre-emit-peephole %s -o - | FileCheck %s
+--- |
+ target datalayout = "e-m:e-i64:64-n32:64"
+ target triple = "powerpc64le-unknown-linux-gnu"
+
+ declare signext i32 @callee(i32 signext) local_unnamed_addr #1
+
+ define signext i32 @func(i32 signext %v) local_unnamed_addr #0 {
+ entry:
+ %call.i = tail call signext i32 @callee(i32 signext %v)
+ %tobool.i = icmp eq i32 %call.i, 0
+ br i1 %tobool.i, label %if.else.i, label %if.then.i
+
+ if.then.i: ; preds = %entry
+ %call2.i = tail call signext i32 @callee(i32 signext %call.i)
+ br label %_Z6calleei.exit
+
+ if.else.i: ; preds = %entry
+ %phitmp = icmp sgt i32 %v, -1
+ br label %_Z6calleei.exit
+
+ _Z6calleei.exit: ; preds = %if.else.i, %if.then.i
+ %call2.i.sink = phi i32 [ %call2.i, %if.then.i ], [ %v, %if.else.i ]
+ %.sink = phi i1 [ false, %if.then.i ], [ %phitmp, %if.else.i ]
+ br i1 %.sink, label %if.end, label %if.then
+
+ if.then: ; preds = %_Z6calleei.exit
+ %call1 = tail call signext i32 @callee(i32 signext 0)
+ br label %if.end
+
+ if.end: ; preds = %if.then, %_Z6calleei.exit
+ ret i32 %call2.i.sink
+ }
+
+ attributes #0 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="ppc64le" "target-features"="+altivec,+bpermd,+crypto,+direct-move,+extdiv,+htm,+power8-vector,+vsx,-power9-vector,-qpx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+ attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="ppc64le" "target-features"="+altivec,+bpermd,+crypto,+direct-move,+extdiv,+htm,+power8-vector,+vsx,-power9-vector,-qpx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+...
+---
+name: func
+alignment: 4
+exposesReturnsTwice: false
+legalized: false
+regBankSelected: false
+selected: false
+failedISel: false
+tracksRegLiveness: true
+registers:
+liveins:
+ - { reg: '$x3', virtual-reg: '' }
+frameInfo:
+ isFrameAddressTaken: false
+ isReturnAddressTaken: false
+ hasStackMap: false
+ hasPatchPoint: false
+ stackSize: 48
+ offsetAdjustment: 0
+ maxAlignment: 0
+ adjustsStack: true
+ hasCalls: true
+ stackProtector: ''
+ maxCallFrameSize: 32
+ hasOpaqueSPAdjustment: false
+ hasVAStart: false
+ hasMustTailInVarArgFunc: false
+ localFrameSize: 0
+ savePoint: ''
+ restorePoint: ''
+fixedStack:
+ - { id: 0, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: 0,
+ callee-saved-register: '$x30', callee-saved-restored: true, debug-info-variable: '',
+ debug-info-expression: '', debug-info-location: '' }
+stack:
+constants:
+
+body: |
+ bb.0.entry:
+ successors: %bb.2(0x30000000), %bb.1(0x50000000)
+ liveins: $x3, $x30
+
+ ; bc and crxor (CRUNSET) should be removed.
+ ; CHECK-LABEL: func
+ ; CHECK: # %bb.1
+ ; CHECK-NOT: crxor
+ ; CHECK-NOT: bc
+ ; CHECK: .LBB0_2
+
+ $x0 = MFLR8 implicit $lr8
+ STD killed $x0, 16, $x1
+ $x1 = STDU $x1, -48, $x1
+ STD killed $x30, 32, $x1 :: (store 8 into %fixed-stack.0, align 16)
+ $x30 = OR8 $x3, $x3
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
+ renamable $cr0 = CMPLWI renamable $r3, 0
+ BCC 76, killed renamable $cr0, %bb.2
+
+ bb.1.if.then.i:
+ successors: %bb.5(0x40000000), %bb.4(0x40000000)
+ liveins: $x3
+
+ renamable $x3 = EXTSW_32_64 killed renamable $r3, implicit $x3
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
+ renamable $cr0gt = CRUNSET implicit-def $cr0
+ $x30 = OR8 killed $x3, $x3
+ BC killed renamable $cr0gt, %bb.5
+
+ bb.4.if.then:
+ successors: %bb.5(0x80000000)
+ liveins: $x30
+
+ $x3 = LI8 0
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def dead $x3
+
+ bb.5.if.end:
+ liveins: $x30
+
+ renamable $x3 = EXTSW_32_64 killed renamable $r30, implicit $x30
+ $x30 = LD 32, $x1 :: (load 8 from %fixed-stack.0, align 16)
+ $x1 = ADDI8 $x1, 48
+ $x0 = LD 16, $x1
+ MTLR8 killed $x0, implicit-def $lr8
+ BLR8 implicit $lr8, implicit $rm, implicit killed $x3
+
+ bb.2.if.else.i:
+ successors: %bb.5(0x40000000), %bb.4(0x40000000)
+ liveins: $x30
+
+ renamable $cr0 = CMPWI renamable $r30, -1
+ BCn killed renamable $cr0gt, %bb.4
+ B %bb.5
+
+...
Added: llvm/trunk/test/CodeGen/PowerPC/setcr_bc2.mir
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/setcr_bc2.mir?rev=343100&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/setcr_bc2.mir (added)
+++ llvm/trunk/test/CodeGen/PowerPC/setcr_bc2.mir Wed Sep 26 05:32:45 2018
@@ -0,0 +1,132 @@
+# RUN: llc -verify-machineinstrs -start-before=ppc-pre-emit-peephole %s -o - | FileCheck %s
+--- |
+ target datalayout = "e-m:e-i64:64-n32:64"
+ target triple = "powerpc64le-unknown-linux-gnu"
+
+ declare signext i32 @callee(i32 signext) local_unnamed_addr #1
+
+ define signext i32 @func(i32 signext %v) local_unnamed_addr #0 {
+ entry:
+ %call.i = tail call signext i32 @callee(i32 signext %v)
+ %tobool.i = icmp eq i32 %call.i, 0
+ br i1 %tobool.i, label %if.else.i, label %if.then.i
+
+ if.then.i: ; preds = %entry
+ %call2.i = tail call signext i32 @callee(i32 signext %call.i)
+ br label %_Z6calleei.exit
+
+ if.else.i: ; preds = %entry
+ %phitmp = icmp sgt i32 %v, -1
+ br label %_Z6calleei.exit
+
+ _Z6calleei.exit: ; preds = %if.else.i, %if.then.i
+ %call2.i.sink = phi i32 [ %call2.i, %if.then.i ], [ %v, %if.else.i ]
+ %.sink = phi i1 [ false, %if.then.i ], [ %phitmp, %if.else.i ]
+ br i1 %.sink, label %if.end, label %if.then
+
+ if.then: ; preds = %_Z6calleei.exit
+ %call1 = tail call signext i32 @callee(i32 signext 0)
+ br label %if.end
+
+ if.end: ; preds = %if.then, %_Z6calleei.exit
+ ret i32 %call2.i.sink
+ }
+
+ attributes #0 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="ppc64le" "target-features"="+altivec,+bpermd,+crypto,+direct-move,+extdiv,+htm,+power8-vector,+vsx,-power9-vector,-qpx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+ attributes #1 = { "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "no-infs-fp-math"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "target-cpu"="ppc64le" "target-features"="+altivec,+bpermd,+crypto,+direct-move,+extdiv,+htm,+power8-vector,+vsx,-power9-vector,-qpx" "unsafe-fp-math"="false" "use-soft-float"="false" }
+
+...
+---
+name: func
+alignment: 4
+exposesReturnsTwice: false
+legalized: false
+regBankSelected: false
+selected: false
+failedISel: false
+tracksRegLiveness: true
+registers:
+liveins:
+ - { reg: '$x3', virtual-reg: '' }
+frameInfo:
+ isFrameAddressTaken: false
+ isReturnAddressTaken: false
+ hasStackMap: false
+ hasPatchPoint: false
+ stackSize: 48
+ offsetAdjustment: 0
+ maxAlignment: 0
+ adjustsStack: true
+ hasCalls: true
+ stackProtector: ''
+ maxCallFrameSize: 32
+ hasOpaqueSPAdjustment: false
+ hasVAStart: false
+ hasMustTailInVarArgFunc: false
+ localFrameSize: 0
+ savePoint: ''
+ restorePoint: ''
+fixedStack:
+ - { id: 0, type: spill-slot, offset: -16, size: 8, alignment: 16, stack-id: 0,
+ callee-saved-register: '$x30', callee-saved-restored: true, debug-info-variable: '',
+ debug-info-expression: '', debug-info-location: '' }
+stack:
+constants:
+
+body: |
+ bb.0.entry:
+ successors: %bb.2(0x30000000), %bb.1(0x50000000)
+ liveins: $x3, $x30
+
+ ; bc should be converted into b, but creqv (CRSET) should not be removed since it is used in a predecessor.
+ ; CHECK-LABEL: func
+ ; CHECK: # %bb.1
+ ; CHECK: creqv
+ ; CHECK-NOT: bc
+ ; CHECK: .LBB0_2
+
+ $x0 = MFLR8 implicit $lr8
+ STD killed $x0, 16, $x1
+ $x1 = STDU $x1, -48, $x1
+ STD killed $x30, 32, $x1 :: (store 8 into %fixed-stack.0, align 16)
+ $x30 = OR8 $x3, $x3
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
+ renamable $cr0 = CMPLWI renamable $r3, 0
+ BCC 76, killed renamable $cr0, %bb.2
+
+ bb.1.if.then.i:
+ successors: %bb.5(0x40000000), %bb.4(0x40000000)
+ liveins: $x3
+
+ renamable $x3 = EXTSW_32_64 killed renamable $r3, implicit $x3
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def $x3
+ renamable $cr0gt = CRSET implicit-def $cr0
+ $x30 = OR8 killed $x3, $x3
+ BC killed renamable $cr0gt, %bb.5
+
+ bb.4.if.then:
+ successors: %bb.5(0x80000000)
+ liveins: $x30
+
+ $x3 = LI8 0
+ BL8_NOP @callee, csr_svr464_altivec, implicit-def dead $lr8, implicit $rm, implicit killed $x3, implicit $x2, implicit-def $r1, implicit-def dead $x3
+
+ bb.5.if.end:
+ liveins: $x30, $cr0gt
+
+ renamable $x3 = EXTSW_32_64 killed renamable $r30, implicit $x30
+ $x30 = LD 32, $x1 :: (load 8 from %fixed-stack.0, align 16)
+ $x1 = ADDI8 $x1, 48
+ $x0 = LD 16, $x1
+ MTLR8 killed $x0, implicit-def $lr8
+ BLR8 implicit $lr8, implicit $rm, implicit killed $x3
+
+ bb.2.if.else.i:
+ successors: %bb.5(0x40000000), %bb.4(0x40000000)
+ liveins: $x30
+
+ renamable $cr0 = CMPWI renamable $r30, -1
+ BCn killed renamable $cr0gt, %bb.4
+ B %bb.5
+
+...
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