Merge pull request #79 from parched/rust-smulo

Fix signed multiplication with overflow

Author: alexcrichton

lib/CodeGen/SelectionDAG/LegalizeDAG.cpp

@@ -3494,11 +3494,11 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
       // part.
       unsigned LoSize = VT.getSizeInBits();
       SDValue HiLHS =
-          DAG.getNode(ISD::SRA, dl, VT, RHS,
+          DAG.getNode(ISD::SRA, dl, VT, LHS,
                       DAG.getConstant(LoSize - 1, dl,
                                       TLI.getPointerTy(DAG.getDataLayout())));
       SDValue HiRHS =
-          DAG.getNode(ISD::SRA, dl, VT, LHS,
+          DAG.getNode(ISD::SRA, dl, VT, RHS,
                       DAG.getConstant(LoSize - 1, dl,
                                       TLI.getPointerTy(DAG.getDataLayout())));
 

test/CodeGen/ARM/v6m-smul-with-overflow.ll

@@ -0,0 +1,16 @@
+; RUN: llc < %s -mtriple=thumbv6m-none-eabi | FileCheck %s
+
+define i1 @signed_multiplication_did_overflow(i32, i32) {
+; CHECK-LABEL: signed_multiplication_did_overflow:
+entry-block:
+  %2 = tail call { i32, i1 } @llvm.smul.with.overflow.i32(i32 %0, i32 %1)
+  %3 = extractvalue { i32, i1 } %2, 1
+  ret i1 %3
+
+; CHECK: mov    r2, r1
+; CHECK: asrs   r1, r0, #31
+; CHECK: asrs   r3, r2, #31
+; CHECK: bl     __aeabi_lmul
+}
+
+declare { i32, i1 } @llvm.smul.with.overflow.i32(i32, i32)