Fix handling of vaargs on PPC32 when going from regsave to overflow.

It can happen that when we only have 1 more register left in the regsave
area we need to store a value bigger than 1 register and therefore we
go to the overflow area. In this case we have to leave the last slot
in the regsave area unused and keep using overflow area. Do this
by storing a limit value to the used register counter in the overflow block.

Issue diagnosed by and solution tested by Mark Millard!

llvm-svn: 261422

1 files changed, 4 insertions, 1 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index bbc6b3b1ae2..8a5cc6c3df8 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -3505,6 +3505,7 @@ public:
 
 Address PPC32_SVR4_ABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAList,
                                       QualType Ty) const {
+  const unsigned OverflowLimit = 8;
   if (const ComplexType *CTy = Ty->getAs<ComplexType>()) {
     // TODO: Implement this. For now ignore.
     (void)CTy;
@@ -3547,7 +3548,7 @@ Address PPC32_SVR4_ABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAList,
   }
 
   llvm::Value *CC =
-      Builder.CreateICmpULT(NumRegs, Builder.getInt8(8), "cond");
+      Builder.CreateICmpULT(NumRegs, Builder.getInt8(OverflowLimit), "cond");
 
   llvm::BasicBlock *UsingRegs = CGF.createBasicBlock("using_regs");
   llvm::BasicBlock *UsingOverflow = CGF.createBasicBlock("using_overflow");
@@ -3599,6 +3600,8 @@ Address PPC32_SVR4_ABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAList,
   {
     CGF.EmitBlock(UsingOverflow);
 
+    Builder.CreateStore(Builder.getInt8(OverflowLimit), NumRegsAddr);
+
     // Everything in the overflow area is rounded up to a size of at least 4.
     CharUnits OverflowAreaAlign = CharUnits::fromQuantity(4);