[ArgPromotion] Add alignment test (NFC)

This shows a miscompile in the current argpromotion implementation:
We may speculatively execute overaligned loads.

Author: nikic

llvm/test/Transforms/ArgumentPromotion/align.ll

@@ -0,0 +1,84 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --function-signature --scrub-attributes
+; RUN: opt -S -argpromotion < %s | FileCheck %s
+
+define internal i32 @callee_must_exec(i32* %p) {
+; CHECK-LABEL: define {{[^@]+}}@callee_must_exec
+; CHECK-SAME: (i32 [[P_VAL:%.*]]) {
+; CHECK-NEXT:    ret i32 [[P_VAL]]
+;
+  %x = load i32, i32* %p, align 16
+  ret i32 %x
+}
+
+define void @caller_must_exec(i32* %p) {
+; CHECK-LABEL: define {{[^@]+}}@caller_must_exec
+; CHECK-SAME: (i32* [[P:%.*]]) {
+; CHECK-NEXT:    [[P_VAL:%.*]] = load i32, i32* [[P]], align 16
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @callee_must_exec(i32 [[P_VAL]])
+; CHECK-NEXT:    ret void
+;
+  call i32 @callee_must_exec(i32* %p)
+  ret void
+}
+
+define internal i32 @callee_guaranteed_aligned(i1 %c, i32* %p) {
+; CHECK-LABEL: define {{[^@]+}}@callee_guaranteed_aligned
+; CHECK-SAME: (i1 [[C:%.*]], i32 [[P_VAL:%.*]]) {
+; CHECK-NEXT:    br i1 [[C]], label [[IF:%.*]], label [[ELSE:%.*]]
+; CHECK:       if:
+; CHECK-NEXT:    ret i32 [[P_VAL]]
+; CHECK:       else:
+; CHECK-NEXT:    ret i32 -1
+;
+  br i1 %c, label %if, label %else
+
+if:
+  %x = load i32, i32* %p, align 16
+  ret i32 %x
+
+else:
+  ret i32 -1
+}
+
+define void @caller_guaranteed_aligned(i1 %c, i32* align 16 dereferenceable(4) %p) {
+; CHECK-LABEL: define {{[^@]+}}@caller_guaranteed_aligned
+; CHECK-SAME: (i1 [[C:%.*]], i32* align 16 dereferenceable(4) [[P:%.*]]) {
+; CHECK-NEXT:    [[P_VAL:%.*]] = load i32, i32* [[P]], align 16
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @callee_guaranteed_aligned(i1 [[C]], i32 [[P_VAL]])
+; CHECK-NEXT:    ret void
+;
+  call i32 @callee_guaranteed_aligned(i1 %c, i32* %p)
+  ret void
+}
+
+; TODO: This should not be promoted, as the caller only guarantees that the
+; pointer is dereferenceable, not that it is aligned.
+define internal i32 @callee_not_guaranteed_aligned(i1 %c, i32* %p) {
+; CHECK-LABEL: define {{[^@]+}}@callee_not_guaranteed_aligned
+; CHECK-SAME: (i1 [[C:%.*]], i32 [[P_VAL:%.*]]) {
+; CHECK-NEXT:    br i1 [[C]], label [[IF:%.*]], label [[ELSE:%.*]]
+; CHECK:       if:
+; CHECK-NEXT:    ret i32 [[P_VAL]]
+; CHECK:       else:
+; CHECK-NEXT:    ret i32 -1
+;
+  br i1 %c, label %if, label %else
+
+if:
+  %x = load i32, i32* %p, align 16
+  ret i32 %x
+
+else:
+  ret i32 -1
+}
+
+define void @caller_not_guaranteed_aligned(i1 %c, i32* dereferenceable(4) %p) {
+; CHECK-LABEL: define {{[^@]+}}@caller_not_guaranteed_aligned
+; CHECK-SAME: (i1 [[C:%.*]], i32* dereferenceable(4) [[P:%.*]]) {
+; CHECK-NEXT:    [[P_VAL:%.*]] = load i32, i32* [[P]], align 16
+; CHECK-NEXT:    [[TMP1:%.*]] = call i32 @callee_not_guaranteed_aligned(i1 [[C]], i32 [[P_VAL]])
+; CHECK-NEXT:    ret void
+;
+  call i32 @callee_not_guaranteed_aligned(i1 %c, i32* %p)
+  ret void
+}