return;
}
+ // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
+ // the bits of its aliasee.
+ if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
+ if (GA->mayBeOverridden()) {
+ KnownZero.clearAllBits(); KnownOne.clearAllBits();
+ } else {
+ computeKnownBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1, Q);
+ }
+ return;
+ }
+
// The address of an aligned GlobalValue has trailing zeros.
if (GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
unsigned Align = GV->getAlignment();
KnownOne.clearAllBits();
return;
}
- // A weak GlobalAlias is totally unknown. A non-weak GlobalAlias has
- // the bits of its aliasee.
- if (GlobalAlias *GA = dyn_cast<GlobalAlias>(V)) {
- if (GA->mayBeOverridden()) {
- KnownZero.clearAllBits(); KnownOne.clearAllBits();
- } else {
- computeKnownBits(GA->getAliasee(), KnownZero, KnownOne, TD, Depth+1, Q);
- }
- return;
- }
if (Argument *A = dyn_cast<Argument>(V)) {
unsigned Align = A->getType()->isPointerTy() ? A->getParamAlignment() : 0;
--- /dev/null
+; RUN: opt -S < %s -instcombine | FileCheck %s
+
+target datalayout = "e-p1:16:16-p2:32:32-p3:64:64"
+
+@G1 = global i32 42, align 1
+@G2 = global i32 42
+@G3 = global [4 x i8] zeroinitializer, align 1
+
+@A1 = alias bitcast (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 2) to i32*)
+@A2 = alias inttoptr (i64 and (i64 ptrtoint (i8* getelementptr inbounds ([4 x i8]* @G3, i32 0, i32 3) to i64), i64 -4) to i32*)
+
+define i64 @f1() {
+; This cannot be constant folded because G1 is underaligned.
+; CHECK-LABEL: @f1(
+; CHECK: ret i64 and
+ ret i64 and (i64 ptrtoint (i32* @G1 to i64), i64 1)
+}
+
+define i64 @f2() {
+; The preferred alignment for G2 allows this one to foled to zero.
+; CHECK-LABEL: @f2(
+; CHECK: ret i64 0
+ ret i64 and (i64 ptrtoint (i32* @G2 to i64), i64 1)
+}
+
+define i64 @g1() {
+; This cannot be constant folded because A1 aliases G3 which is underalaigned.
+; CHECK-LABEL: @g1(
+; CHECK: ret i64 and
+ ret i64 and (i64 ptrtoint (i32* @A1 to i64), i64 1)
+}
+
+define i64 @g2() {
+; While A2 also aliases G3 which is underaligned, the math of A2 forces a
+; certain alignment allowing this to fold to zero.
+; CHECK-LABEL: @g2(
+; CHECK: ret i64 0
+ ret i64 and (i64 ptrtoint (i32* @A2 to i64), i64 1)
+}
+