The alignment of an sret parameter is known: it must be at least the
alignment of the return type. Teach the optimizers this.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@165226 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/docs/LangRef.html b/docs/LangRef.html
index 89b9227..7ee1418 100644
--- a/docs/LangRef.html
+++ b/docs/LangRef.html
@@ -1107,9 +1107,9 @@
<dd>This indicates that the pointer parameter specifies the address of a
structure that is the return value of the function in the source program.
This pointer must be guaranteed by the caller to be valid: loads and
- stores to the structure may be assumed by the callee to not to trap. This
- may only be applied to the first parameter. This is not a valid attribute
- for return values. </dd>
+ stores to the structure may be assumed by the callee to not to trap and
+ to be properly aligned. This may only be applied to the first parameter.
+ This is not a valid attribute for return values. </dd>
<dt><tt><b><a name="noalias">noalias</a></b></tt></dt>
<dd>This indicates that pointer values
diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index 491224a..1004ebc 100644
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -308,11 +308,20 @@
}
if (Argument *A = dyn_cast<Argument>(V)) {
- // Get alignment information off byval arguments if specified in the IR.
- if (A->hasByValAttr())
- if (unsigned Align = A->getParamAlignment())
- KnownZero = APInt::getLowBitsSet(BitWidth,
- CountTrailingZeros_32(Align));
+ unsigned Align = 0;
+
+ if (A->hasByValAttr()) {
+ // Get alignment information off byval arguments if specified in the IR.
+ Align = A->getParamAlignment();
+ } else if (TD && A->hasStructRetAttr()) {
+ // An sret parameter has at least the ABI alignment of the return type.
+ Type *EltTy = cast<PointerType>(A->getType())->getElementType();
+ if (EltTy->isSized())
+ Align = TD->getABITypeAlignment(EltTy);
+ }
+
+ if (Align)
+ KnownZero = APInt::getLowBitsSet(BitWidth, CountTrailingZeros_32(Align));
return;
}
diff --git a/test/Transforms/InstCombine/align-addr.ll b/test/Transforms/InstCombine/align-addr.ll
index 27916b9..4ea1bd9 100644
--- a/test/Transforms/InstCombine/align-addr.ll
+++ b/test/Transforms/InstCombine/align-addr.ll
@@ -58,3 +58,19 @@
store double %n, double* %p
ret double %t
}
+
+declare void @llvm.memset.p0i8.i64(i8* nocapture, i8, i64, i32, i1) nounwind
+
+declare void @use(i8*)
+
+%struct.s = type { i32, i32, i32, i32 }
+
+define void @test3(%struct.s* sret %a4) {
+; Check that the alignment is bumped up the alignment of the sret type.
+; CHECK: @test3
+ %a4.cast = bitcast %struct.s* %a4 to i8*
+ call void @llvm.memset.p0i8.i64(i8* %a4.cast, i8 0, i64 16, i32 1, i1 false)
+; CHECK: call void @llvm.memset.p0i8.i64(i8* %a4.cast, i8 0, i64 16, i32 4, i1 false)
+ call void @use(i8* %a4.cast)
+ ret void
+}