[AArch64] Correct the check of signed 9-bit imm in getIndexedAddressParts()

[haicheng]

Summary

-256 is a legal indexed address part.

[efriedma]

lib/Target/AArch64/AArch64ISelLowering.cpp

10248

This has undefined behavior if RHCS == INT64_MIN.

[haicheng]

Address Eli's comment. Thank you.

[rengolin]

Seems like an obvious fix. Can you also add tests at the boundary where they shouldn't be encoded in 9-bit form?

[haicheng]

Add more tests as requested by Renato. Thank you.

[rengolin]

LGTM. Thanks!

lib/Target/AArch64/AArch64ISelLowering.cpp

bool AArch64TargetLowering::getIndexedAddressParts(SDNode *Op, SDValue &Base,
                                                    SelectionDAG &DAG) const {
   if (Op->getOpcode() != ISD::ADD && Op->getOpcode() != ISD::SUB)
     return false;
 
   Base = Op->getOperand(0);
   // All of the indexed addressing mode instructions take a signed
   // 9 bit immediate offset.
   if (ConstantSDNode *RHS = dyn_cast<ConstantSDNode>(Op->getOperand(1))) {
-    int64_t RHSC = (int64_t)RHS->getZExtValue();
-    if (RHSC >= 256 || RHSC <= -256)
+    int64_t RHSC = RHS->getSExtValue();
+    if (Op->getOpcode() == ISD::SUB)
+      RHSC *= -1;
+    if (!isInt<9>(RHSC))
       return false;
     IsInc = (Op->getOpcode() == ISD::ADD);
     Offset = Op->getOperand(1);
     return true;
   }
   return false;
 }
 

test/CodeGen/AArch64/arm64-indexed-memory.ll

 ; RUN: llc < %s -mtriple=arm64-eabi -aarch64-redzone | FileCheck %s
 
 define void @store64(i64** nocapture %out, i64 %index, i64 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: store64:
 ; CHECK: str x{{[0-9+]}}, [x{{[0-9+]}}], #8
 ; CHECK: ret
   %tmp = load i64*, i64** %out, align 8
   %incdec.ptr = getelementptr inbounds i64, i64* %tmp, i64 1
   store i64 %spacing, i64* %tmp, align 4
   store i64* %incdec.ptr, i64** %out, align 8
   ret void
 }
 
+define void @store64idxneg256(i64** nocapture %out, i64 %index, i64 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: store64idxneg256:
+; CHECK: str x{{[0-9+]}}, [x{{[0-9+]}}], #-256
+; CHECK: ret
+  %tmp = load i64*, i64** %out, align 8
+  %incdec.ptr = getelementptr inbounds i64, i64* %tmp, i64 -32
+  store i64 %spacing, i64* %tmp, align 4
+  store i64* %incdec.ptr, i64** %out, align 8
+  ret void
+}
+
 define void @store32(i32** nocapture %out, i32 %index, i32 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: store32:
 ; CHECK: str w{{[0-9+]}}, [x{{[0-9+]}}], #4
 ; CHECK: ret
   %tmp = load i32*, i32** %out, align 8
   %incdec.ptr = getelementptr inbounds i32, i32* %tmp, i64 1
   store i32 %spacing, i32* %tmp, align 4
   store i32* %incdec.ptr, i32** %out, align 8
   ret void
 }
 
+define void @store32idxneg256(i32** nocapture %out, i32 %index, i32 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: store32idxneg256:
+; CHECK: str w{{[0-9+]}}, [x{{[0-9+]}}], #-256
+; CHECK: ret
+  %tmp = load i32*, i32** %out, align 8
+  %incdec.ptr = getelementptr inbounds i32, i32* %tmp, i64 -64
+  store i32 %spacing, i32* %tmp, align 4
+  store i32* %incdec.ptr, i32** %out, align 8
+  ret void
+}
+
 define void @store16(i16** nocapture %out, i16 %index, i16 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: store16:
 ; CHECK: strh w{{[0-9+]}}, [x{{[0-9+]}}], #2
 ; CHECK: ret
   %tmp = load i16*, i16** %out, align 8
   %incdec.ptr = getelementptr inbounds i16, i16* %tmp, i64 1
   store i16 %spacing, i16* %tmp, align 4
   store i16* %incdec.ptr, i16** %out, align 8
   ret void
 }
 
+define void @store16idxneg256(i16** nocapture %out, i16 %index, i16 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: store16idxneg256:
+; CHECK: strh w{{[0-9+]}}, [x{{[0-9+]}}], #-256
+; CHECK: ret
+  %tmp = load i16*, i16** %out, align 8
+  %incdec.ptr = getelementptr inbounds i16, i16* %tmp, i64 -128
+  store i16 %spacing, i16* %tmp, align 4
+  store i16* %incdec.ptr, i16** %out, align 8
+  ret void
+}
+
 define void @store8(i8** nocapture %out, i8 %index, i8 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: store8:
 ; CHECK: strb w{{[0-9+]}}, [x{{[0-9+]}}], #1
 ; CHECK: ret
   %tmp = load i8*, i8** %out, align 8
   %incdec.ptr = getelementptr inbounds i8, i8* %tmp, i64 1
   store i8 %spacing, i8* %tmp, align 4
   store i8* %incdec.ptr, i8** %out, align 8
   ret void
 }
 
+define void @store8idxneg256(i8** nocapture %out, i8 %index, i8 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: store8idxneg256:
+; CHECK: strb w{{[0-9+]}}, [x{{[0-9+]}}], #-256
+; CHECK: ret
+  %tmp = load i8*, i8** %out, align 8
+  %incdec.ptr = getelementptr inbounds i8, i8* %tmp, i64 -256
+  store i8 %spacing, i8* %tmp, align 4
+  store i8* %incdec.ptr, i8** %out, align 8
+  ret void
+}
+
 define void @truncst64to32(i32** nocapture %out, i32 %index, i64 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: truncst64to32:
 ; CHECK: str w{{[0-9+]}}, [x{{[0-9+]}}], #4
 ; CHECK: ret
   %tmp = load i32*, i32** %out, align 8
   %incdec.ptr = getelementptr inbounds i32, i32* %tmp, i64 1
   %trunc = trunc i64 %spacing to i32
   store i32 %trunc, i32* %tmp, align 4

 ; CHECK-NEXT: str     x1, [x0, #16]!
 ; CHECK-NEXT: ret
   %tmp = load i64*, i64** %out, align 8
   %ptr = getelementptr inbounds i64, i64* %tmp, i64 2
   store i64 %spacing, i64* %ptr, align 4
   ret i64 *%ptr
 }
 
+define i64 * @pre64idxneg256(i64** nocapture %out, i64 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: pre64idxneg256:
+; CHECK: ldr     x0, [x0]
+; CHECK-NEXT: str     x1, [x0, #-256]!
+; CHECK-NEXT: ret
+  %tmp = load i64*, i64** %out, align 8
+  %ptr = getelementptr inbounds i64, i64* %tmp, i64 -32
+  store i64 %spacing, i64* %ptr, align 4
+  ret i64 *%ptr
+}
+
 define i32 * @pre32(i32** nocapture %out, i32 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: pre32:
 ; CHECK: ldr     x0, [x0]
 ; CHECK-NEXT: str     w1, [x0, #8]!
 ; CHECK-NEXT: ret
   %tmp = load i32*, i32** %out, align 8
   %ptr = getelementptr inbounds i32, i32* %tmp, i64 2
   store i32 %spacing, i32* %ptr, align 4
   ret i32 *%ptr
 }
 
+define i32 * @pre32idxneg256(i32** nocapture %out, i32 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: pre32idxneg256:
+; CHECK: ldr     x0, [x0]
+; CHECK-NEXT: str     w1, [x0, #-256]!
+; CHECK-NEXT: ret
+  %tmp = load i32*, i32** %out, align 8
+  %ptr = getelementptr inbounds i32, i32* %tmp, i64 -64
+  store i32 %spacing, i32* %ptr, align 4
+  ret i32 *%ptr
+}
+
 define i16 * @pre16(i16** nocapture %out, i16 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: pre16:
 ; CHECK: ldr     x0, [x0]
 ; CHECK-NEXT: strh    w1, [x0, #4]!
 ; CHECK-NEXT: ret
   %tmp = load i16*, i16** %out, align 8
   %ptr = getelementptr inbounds i16, i16* %tmp, i64 2
   store i16 %spacing, i16* %ptr, align 4
   ret i16 *%ptr
 }
 
+define i16 * @pre16idxneg256(i16** nocapture %out, i16 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: pre16idxneg256:
+; CHECK: ldr     x0, [x0]
+; CHECK-NEXT: strh    w1, [x0, #-256]!
+; CHECK-NEXT: ret
+  %tmp = load i16*, i16** %out, align 8
+  %ptr = getelementptr inbounds i16, i16* %tmp, i64 -128
+  store i16 %spacing, i16* %ptr, align 4
+  ret i16 *%ptr
+}
+
 define i8 * @pre8(i8** nocapture %out, i8 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: pre8:
 ; CHECK: ldr     x0, [x0]
 ; CHECK-NEXT: strb    w1, [x0, #2]!
 ; CHECK-NEXT: ret
   %tmp = load i8*, i8** %out, align 8
   %ptr = getelementptr inbounds i8, i8* %tmp, i64 2
   store i8 %spacing, i8* %ptr, align 4
   ret i8 *%ptr
 }
 
+define i8 * @pre8idxneg256(i8** nocapture %out, i8 %spacing) nounwind noinline ssp {
+; CHECK-LABEL: pre8idxneg256:
+; CHECK: ldr     x0, [x0]
+; CHECK-NEXT: strb    w1, [x0, #-256]!
+; CHECK-NEXT: ret
+  %tmp = load i8*, i8** %out, align 8
+  %ptr = getelementptr inbounds i8, i8* %tmp, i64 -256
+  store i8 %spacing, i8* %ptr, align 4
+  ret i8 *%ptr
+}
+
 define i32 * @pretrunc64to32(i32** nocapture %out, i64 %spacing) nounwind noinline ssp {
 ; CHECK-LABEL: pretrunc64to32:
 ; CHECK: ldr     x0, [x0]
 ; CHECK-NEXT: str     w1, [x0, #8]!
 ; CHECK-NEXT: ret
   %tmp = load i32*, i32** %out, align 8
   %ptr = getelementptr inbounds i32, i32* %tmp, i64 2
   %trunc = trunc i64 %spacing to i32