[ARM] Do not assume memory intrinsics specify alignment. (#138356)

Author: hvdijk

llvm/lib/Target/ARM/ARMTargetTransformInfo.cpp

@@ -1169,8 +1169,8 @@ int ARMTTIImpl::getNumMemOps(const IntrinsicInst *I) const {
       return -1;
 
     const unsigned Size = C->getValue().getZExtValue();
-    const Align DstAlign = *MC->getDestAlign();
-    const Align SrcAlign = *MC->getSourceAlign();
+    const Align DstAlign = MC->getDestAlign().valueOrOne();
+    const Align SrcAlign = MC->getSourceAlign().valueOrOne();
 
     MOp = MemOp::Copy(Size, /*DstAlignCanChange*/ false, DstAlign, SrcAlign,
                       /*IsVolatile*/ false);
@@ -1184,7 +1184,7 @@ int ARMTTIImpl::getNumMemOps(const IntrinsicInst *I) const {
       return -1;
 
     const unsigned Size = C->getValue().getZExtValue();
-    const Align DstAlign = *MS->getDestAlign();
+    const Align DstAlign = MS->getDestAlign().valueOrOne();
 
     MOp = MemOp::Set(Size, /*DstAlignCanChange*/ false, DstAlign,
                      /*IsZeroMemset*/ false, /*IsVolatile*/ false);

llvm/test/Analysis/CostModel/ARM/memcpy.ll

@@ -11,6 +11,22 @@ target triple = "thumbv7m-arm-unknown-eabi"
 ; Align 1, 1
 ;;;;;;;;;;;;
 
+define void @memcpy_0(ptr %d, ptr %s) {
+;
+; with/without strict-align:
+;
+; ldrb r1, [r1]
+; strb r1, [r0]
+;
+; COMMON-LABEL: 'memcpy_0'
+; COMMON-NEXT:  Cost Model: Found an estimated cost of 2 for instruction: call void @llvm.memcpy.p0.p0.i32(ptr %d, ptr %s, i32 1, i1 false)
+; COMMON-NEXT:  Cost Model: Found an estimated cost of 1 for instruction: ret void
+;
+entry:
+  call void @llvm.memcpy.p0.p0.i32(ptr %d, ptr %s, i32 1, i1 false)
+  ret void
+}
+
 define void @memcpy_1(ptr %d, ptr %s) {
 ;
 ; with/without strict-align: