[CodeGen][va_args] Correct Vector Struct va-arg 'in_reg' code gen

When trying to track down a different bug, we discovered
that calling __builtin_va_arg on a vec3f type caused
the SROA pass to issue a warning that there was an illegal
access.

Further research showed that the vec3f type is
alloca'ed as size '12', but the _builtin_va_arg code
on x86_64 was always loading this out of registers as
{double, double}. Thus, the 2nd store into the vec3f
was storing in bytes 12-15!

This patch alters the original implementation which always
assumed {double, double} to use the actual coerced type
instead, so the LLVM-IR generated is a load/GEP/store of
a <2 x float> and a float, rather than a double and a double.

Tests were added for all combinations I could think of that
would fit in 2 FP registers, and all work exactly as expected.

Differential Revision: https://reviews.llvm.org/D42811

llvm-svn: 324098

1 files changed, 7 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/TargetInfo.cpp b/clang/lib/CodeGen/TargetInfo.cpp
index 8641d87..f523096 100644
--- a/clang/lib/CodeGen/TargetInfo.cpp
+++ b/clang/lib/CodeGen/TargetInfo.cpp
@@ -3790,17 +3790,18 @@ Address X86_64ABIInfo::EmitVAArg(CodeGenFunction &CGF, Address VAListAddr,
     Address RegAddrHi =
       CGF.Builder.CreateConstInBoundsByteGEP(RegAddrLo,
                                              CharUnits::fromQuantity(16));
-    llvm::Type *DoubleTy = CGF.DoubleTy;
-    llvm::StructType *ST = llvm::StructType::get(DoubleTy, DoubleTy);
+    llvm::Type *ST = AI.canHaveCoerceToType()
+                         ? AI.getCoerceToType()
+                         : llvm::StructType::get(CGF.DoubleTy, CGF.DoubleTy);
     llvm::Value *V;
     Address Tmp = CGF.CreateMemTemp(Ty);
     Tmp = CGF.Builder.CreateElementBitCast(Tmp, ST);
-    V = CGF.Builder.CreateLoad(
-                   CGF.Builder.CreateElementBitCast(RegAddrLo, DoubleTy));
+    V = CGF.Builder.CreateLoad(CGF.Builder.CreateElementBitCast(
+        RegAddrLo, ST->getStructElementType(0)));
     CGF.Builder.CreateStore(V,
                    CGF.Builder.CreateStructGEP(Tmp, 0, CharUnits::Zero()));
-    V = CGF.Builder.CreateLoad(
-                   CGF.Builder.CreateElementBitCast(RegAddrHi, DoubleTy));
+    V = CGF.Builder.CreateLoad(CGF.Builder.CreateElementBitCast(
+        RegAddrHi, ST->getStructElementType(1)));
     CGF.Builder.CreateStore(V,
           CGF.Builder.CreateStructGEP(Tmp, 1, CharUnits::fromQuantity(8)));