Fix CoerceIntOrPtrToIntOrPtr on big-endian targets.

Type coercion for argument passing is equivalent to storing the source
type and loading the destination type from the same pointer. On
big-endian targets, this means that the high bits of integers are
preserved.

This patch fixes the CoerceIntOrPtrToIntOrPtr() function on big-endian
targets by inserting the required shift instructions to preserve the
high bits instead of the low bits.

This is used by SparcABIInfo when passing small structs in the high bits
of registers.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183291 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp
index 3c079cd58bbe7d9e92c131e1cf3b5e121904fbef..a53283eb143178bf11d82949199ac35197a65331 100644 (file)
--- a/lib/CodeGen/CGCall.cpp
+++ b/lib/CodeGen/CGCall.cpp
@@ -642,6 +642,10 @@ EnterStructPointerForCoercedAccess(llvm::Value *SrcPtr,
 /// CoerceIntOrPtrToIntOrPtr - Convert a value Val to the specific Ty where both
 /// are either integers or pointers.  This does a truncation of the value if it
 /// is too large or a zero extension if it is too small.
+///
+/// This behaves as if the value were coerced through memory, so on big-endian
+/// targets the high bits are preserved in a truncation, while little-endian
+/// targets preserve the low bits.
 static llvm::Value *CoerceIntOrPtrToIntOrPtr(llvm::Value *Val,
                                              llvm::Type *Ty,
                                              CodeGenFunction &CGF) {
@@ -661,8 +665,25 @@ static llvm::Value *CoerceIntOrPtrToIntOrPtr(llvm::Value *Val,
   if (isa<llvm::PointerType>(DestIntTy))
     DestIntTy = CGF.IntPtrTy;
 
-  if (Val->getType() != DestIntTy)
-    Val = CGF.Builder.CreateIntCast(Val, DestIntTy, false, "coerce.val.ii");
+  if (Val->getType() != DestIntTy) {
+    const llvm::DataLayout &DL = CGF.CGM.getDataLayout();
+    if (DL.isBigEndian()) {
+      // Preserve the high bits on big-endian targets.
+      // That is what memory coercion does.
+      uint64_t SrcSize = DL.getTypeAllocSizeInBits(Val->getType());
+      uint64_t DstSize = DL.getTypeAllocSizeInBits(DestIntTy);
+      if (SrcSize > DstSize) {
+        Val = CGF.Builder.CreateLShr(Val, SrcSize - DstSize, "coerce.highbits");
+        Val = CGF.Builder.CreateTrunc(Val, DestIntTy, "coerce.val.ii");
+      } else {
+        Val = CGF.Builder.CreateZExt(Val, DestIntTy, "coerce.val.ii");
+        Val = CGF.Builder.CreateShl(Val, DstSize - SrcSize, "coerce.highbits");
+      }
+    } else {
+      // Little-endian targets preserve the low bits. No shifts required.
+      Val = CGF.Builder.CreateIntCast(Val, DestIntTy, false, "coerce.val.ii");
+    }
+  }
 
   if (isa<llvm::PointerType>(Ty))
     Val = CGF.Builder.CreateIntToPtr(Val, Ty, "coerce.val.ip");

diff --git a/test/CodeGen/sparcv9-abi.c b/test/CodeGen/sparcv9-abi.c
index b4c7d6854988e254b55512085956fdcdce35faa2..b58c84689ad220d25739cfadae133f74b003aae0 100644 (file)
--- a/test/CodeGen/sparcv9-abi.c
+++ b/test/CodeGen/sparcv9-abi.c
@@ -85,7 +85,33 @@ struct mixed2 {
   double b;
 };
 
+// CHECK: define { i64, double } @f_mixed2(i64 %x.coerce0, double %x.coerce1)
+// CHECK: store i64 %x.coerce0
+// CHECK: store double %x.coerce1
 struct mixed2 f_mixed2(struct mixed2 x) {
   x.a += 1;
   return x;
 }
+
+// Struct with single element and padding in passed in the high bits of a
+// register.
+struct tiny {
+  char a;
+};
+
+// CHECK: define i64 @f_tiny(i64 %x.coerce)
+// CHECK: %[[HB:[^ ]+]] = lshr i64 %x.coerce, 56
+// CHECK: = trunc i64 %[[HB]] to i8
+struct tiny f_tiny(struct tiny x) {
+  x.a += 1;
+  return x;
+}
+
+// CHECK: define void @call_tiny()
+// CHECK: %[[XV:[^ ]+]] = zext i8 %{{[^ ]+}} to i64
+// CHECK: %[[HB:[^ ]+]] = shl i64 %[[XV]], 56
+// CHECK: = call i64 @f_tiny(i64 %[[HB]])
+void call_tiny() {
+  struct tiny x = { 1 };
+  f_tiny(x);
+}