Recommit "[X86] Increase the number of instructions searched for isSafeToClobberEFLAGS in a couple places"

I messed up the bug numbers in the commit message before

Previously this function searched 4 instructions forwards or
backwards to determine if it was ok to clobber eflags.

This is called in 3 places: rematerialization, turning 2 operand
leas into adds or splitting 3 ops leas into an lea and add on some
CPU targets.

This patch increases the search limit to 10 instructions for
rematerialization and 2 operand lea to add. I've left the old
treshold for 3 ops lea spliting as that increases code size.

Fixes PR47024 and PR46315.

Author: topperc

llvm/lib/Target/X86/X86FixupLEAs.cpp

@@ -376,7 +376,7 @@ bool FixupLEAPass::optTwoAddrLEA(MachineBasicBlock::iterator &I,
   const MachineOperand &Segment = MI.getOperand(1 + X86::AddrSegmentReg);
 
   if (Segment.getReg() != 0 || !Disp.isImm() || Scale.getImm() > 1 ||
-      !TII->isSafeToClobberEFLAGS(MBB, I))
+      !TII->isSafeToClobberEFLAGS(MBB, I, 10))
     return false;
 
   Register DestReg = MI.getOperand(0).getReg();

llvm/lib/Target/X86/X86InstrInfo.cpp

@@ -1127,7 +1127,7 @@ void X86InstrInfo::reMaterialize(MachineBasicBlock &MBB,
                                  const MachineInstr &Orig,
                                  const TargetRegisterInfo &TRI) const {
   bool ClobbersEFLAGS = Orig.modifiesRegister(X86::EFLAGS, &TRI);
-  if (ClobbersEFLAGS && !isSafeToClobberEFLAGS(MBB, I)) {
+  if (ClobbersEFLAGS && !isSafeToClobberEFLAGS(MBB, I, 10)) {
     // The instruction clobbers EFLAGS. Re-materialize as MOV32ri to avoid side
     // effects.
     int Value;

llvm/lib/Target/X86/X86InstrInfo.h

@@ -442,8 +442,9 @@ class X86InstrInfo final : public X86GenInstrInfo {
   /// conservative. If it cannot definitely determine the safety after visiting
   /// a few instructions in each direction it assumes it's not safe.
   bool isSafeToClobberEFLAGS(MachineBasicBlock &MBB,
-                             MachineBasicBlock::iterator I) const {
-    return MBB.computeRegisterLiveness(&RI, X86::EFLAGS, I, 4) ==
+                             MachineBasicBlock::iterator I,
+                             unsigned Neighborhood = 4) const {
+    return MBB.computeRegisterLiveness(&RI, X86::EFLAGS, I, Neighborhood) ==
            MachineBasicBlock::LQR_Dead;
   }
 

llvm/test/CodeGen/X86/optimize-max-0.ll

@@ -85,7 +85,7 @@ define void @foo(i8* %r, i32 %s, i32 %w, i32 %x, i8* %j, i32 %d) nounwind {
 ; CHECK-NEXT:    movl {{[-0-9]+}}(%e{{[sb]}}p), %eax ## 4-byte Reload
 ; CHECK-NEXT:    addl %ecx, %eax
 ; CHECK-NEXT:    movl {{[0-9]+}}(%esp), %esi
-; CHECK-NEXT:    leal 2(%esi), %esi
+; CHECK-NEXT:    addl $2, %esi
 ; CHECK-NEXT:    movl %esi, {{[-0-9]+}}(%e{{[sb]}}p) ## 4-byte Spill
 ; CHECK-NEXT:    movl (%esp), %esi ## 4-byte Reload
 ; CHECK-NEXT:    addl %esi, %ecx
@@ -513,7 +513,7 @@ define void @bar(i8* %r, i32 %s, i32 %w, i32 %x, i8* %j, i32 %d) nounwind {
 ; CHECK-NEXT:    movl {{[-0-9]+}}(%e{{[sb]}}p), %ecx ## 4-byte Reload
 ; CHECK-NEXT:    addl %eax, %ecx
 ; CHECK-NEXT:    movl {{[0-9]+}}(%esp), %edx
-; CHECK-NEXT:    leal 2(%edx), %edx
+; CHECK-NEXT:    addl $2, %edx
 ; CHECK-NEXT:    movl %edx, {{[-0-9]+}}(%e{{[sb]}}p) ## 4-byte Spill
 ; CHECK-NEXT:    movl {{[-0-9]+}}(%e{{[sb]}}p), %edx ## 4-byte Reload
 ; CHECK-NEXT:    addl %edx, %eax

llvm/test/CodeGen/X86/pr47024.ll

@@ -0,0 +1,18 @@
+; NOTE: Assertions have been autogenerated by utils/update_llc_test_checks.py
+; RUN: llc < %s -mtriple=x86_64-unknown-linux-gnu | FileCheck %s
+
+define void @_Z4testv() {
+; CHECK-LABEL: _Z4testv:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movabsq $21542142465, %rdi # imm = 0x504030201
+; CHECK-NEXT:    movabsq $723401749922909195, %rdx # imm = 0xA0A0A0F0E0D0C0B
+; CHECK-NEXT:    movabsq $723401728380766730, %rcx # imm = 0xA0A0A0A0A0A0A0A
+; CHECK-NEXT:    movabsq $1446803478303675925, %r8 # imm = 0x1414141918171615
+; CHECK-NEXT:    movabsq $798285110420182026, %r9 # imm = 0xB1414141414140A
+; CHECK-NEXT:    xorl %esi, %esi
+; CHECK-NEXT:    jmp _Z8process36data_tS_S_ # TAILCALL
+  tail call void @_Z8process36data_tS_S_(i64 21542142465, i64 0, i64 723401749922909195, i64 723401728380766730, i64 1446803478303675925, i64 798285110420182026)
+  ret void
+}
+
+declare void @_Z8process36data_tS_S_(i64, i64, i64, i64, i64, i64)