[X86] Fix stack probing on x32 (PR41477)

Fix for https://bugs.llvm.org/show_bug.cgi?id=41477. On the x32 ABI
with stack probing a dynamic alloca will result in a WIN_ALLOCA_32
with a 32-bit size. The current implementation tries to copy it into
RAX, resulting in a physreg copy error. Fix this by copying to EAX
instead. Also fix incorrect opcodes or registers used in subs.

llvm-svn: 358807

2 files changed, 15 insertions, 8 deletions

diff --git a/llvm/lib/Target/X86/X86FrameLowering.cpp b/llvm/lib/Target/X86/X86FrameLowering.cpp
index 7a28709be7b..581df4345a7 100644
--- a/llvm/lib/Target/X86/X86FrameLowering.cpp
+++ b/llvm/lib/Target/X86/X86FrameLowering.cpp
@@ -794,8 +794,8 @@ void X86FrameLowering::emitStackProbeCall(MachineFunction &MF,
         .addExternalSymbol(MF.createExternalSymbolName(Symbol));
   }
 
-  unsigned AX = Is64Bit ? X86::RAX : X86::EAX;
-  unsigned SP = Is64Bit ? X86::RSP : X86::ESP;
+  unsigned AX = Uses64BitFramePtr ? X86::RAX : X86::EAX;
+  unsigned SP = Uses64BitFramePtr ? X86::RSP : X86::ESP;
   CI.addReg(AX, RegState::Implicit)
       .addReg(SP, RegState::Implicit)
       .addReg(AX, RegState::Define | RegState::Implicit)
@@ -809,7 +809,7 @@ void X86FrameLowering::emitStackProbeCall(MachineFunction &MF,
     // adjusting %rsp.
     // All other platforms do not specify a particular ABI for the stack probe
     // function, so we arbitrarily define it to not adjust %esp/%rsp itself.
-    BuildMI(MBB, MBBI, DL, TII.get(getSUBrrOpcode(Is64Bit)), SP)
+    BuildMI(MBB, MBBI, DL, TII.get(getSUBrrOpcode(Uses64BitFramePtr)), SP)
         .addReg(SP)
         .addReg(AX);
   }
diff --git a/llvm/lib/Target/X86/X86WinAllocaExpander.cpp b/llvm/lib/Target/X86/X86WinAllocaExpander.cpp
index 438c7a5ed69..aa2c872403a 100644
--- a/llvm/lib/Target/X86/X86WinAllocaExpander.cpp
+++ b/llvm/lib/Target/X86/X86WinAllocaExpander.cpp
@@ -209,15 +209,18 @@ void X86WinAllocaExpander::lower(MachineInstr* MI, Lowering L) {
     return;
   }
 
+  // These two variables differ on x32, which is a 64-bit target with a
+  // 32-bit alloca.
   bool Is64Bit = STI->is64Bit();
+  bool Is64BitAlloca = MI->getOpcode() == X86::WIN_ALLOCA_64;
   assert(SlotSize == 4 || SlotSize == 8);
-  unsigned RegA = (SlotSize == 8) ? X86::RAX : X86::EAX;
 
   switch (L) {
-  case TouchAndSub:
+  case TouchAndSub: {
     assert(Amount >= SlotSize);
 
     // Use a push to touch the top of the stack.
+    unsigned RegA = Is64Bit ? X86::RAX : X86::EAX;
     BuildMI(*MBB, I, DL, TII->get(Is64Bit ? X86::PUSH64r : X86::PUSH32r))
         .addReg(RegA, RegState::Undef);
     Amount -= SlotSize;
@@ -226,15 +229,18 @@ void X86WinAllocaExpander::lower(MachineInstr* MI, Lowering L) {
 
     // Fall through to make any remaining adjustment.
     LLVM_FALLTHROUGH;
+  }
   case Sub:
     assert(Amount > 0);
     if (Amount == SlotSize) {
       // Use push to save size.
+      unsigned RegA = Is64Bit ? X86::RAX : X86::EAX;
       BuildMI(*MBB, I, DL, TII->get(Is64Bit ? X86::PUSH64r : X86::PUSH32r))
           .addReg(RegA, RegState::Undef);
     } else {
       // Sub.
-      BuildMI(*MBB, I, DL, TII->get(getSubOpcode(Is64Bit, Amount)), StackPtr)
+      BuildMI(*MBB, I, DL,
+              TII->get(getSubOpcode(Is64BitAlloca, Amount)), StackPtr)
           .addReg(StackPtr)
           .addImm(Amount);
     }
@@ -242,6 +248,7 @@ void X86WinAllocaExpander::lower(MachineInstr* MI, Lowering L) {
   case Probe:
     if (!NoStackArgProbe) {
       // The probe lowering expects the amount in RAX/EAX.
+      unsigned RegA = Is64BitAlloca ? X86::RAX : X86::EAX;
       BuildMI(*MBB, MI, DL, TII->get(TargetOpcode::COPY), RegA)
           .addReg(MI->getOperand(0).getReg());
 
@@ -250,8 +257,8 @@ void X86WinAllocaExpander::lower(MachineInstr* MI, Lowering L) {
                                               /*InPrologue=*/false);
     } else {
       // Sub
-      BuildMI(*MBB, I, DL, TII->get(Is64Bit ? X86::SUB64rr : X86::SUB32rr),
-              StackPtr)
+      BuildMI(*MBB, I, DL,
+              TII->get(Is64BitAlloca ? X86::SUB64rr : X86::SUB32rr), StackPtr)
           .addReg(StackPtr)
           .addReg(MI->getOperand(0).getReg());
     }