From 0a76e3241f05a996a2a507a5c32476326d2b3355 Mon Sep 17 00:00:00 2001
From: Eli Friedman <efriedma@codeaurora.org>
Date: Tue, 6 Dec 2016 22:49:36 +0000
Subject: [PATCH] [CodeGen] Fix result type for SMULO/UMULO legalization

On some platforms (like MSP430) the second element of the result
structure for SMULO/UMULO may have a shorter type than the one
returned by SetCC. We need to truncate it to the right type, or
else some incorrect code may be generated later on.

This fixes issue https://github.com/rust-lang/rust/issues/37829

Patch by Vadzim Dambrouski!

Differential Revision: https://reviews.llvm.org/D27154

llvm-svn: 288857
---
 llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp |  9 ++++++++
 llvm/test/CodeGen/MSP430/umulo-16.ll          | 32 +++++++++++++++++++++++++++
 2 files changed, 41 insertions(+)
 create mode 100644 llvm/test/CodeGen/MSP430/umulo-16.ll

diff --git a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
index d970ff4..7a04e0d 100644
--- a/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/LegalizeDAG.cpp
@@ -3515,6 +3515,15 @@ bool SelectionDAGLegalize::ExpandNode(SDNode *Node) {
       TopHalf = DAG.getSetCC(dl, getSetCCResultType(VT), TopHalf,
                              DAG.getConstant(0, dl, VT), ISD::SETNE);
     }
+
+    // Truncate the result if SetCC returns a larger type than needed.
+    EVT RType = Node->getValueType(1);
+    if (RType.getSizeInBits() < TopHalf.getValueSizeInBits())
+      TopHalf = DAG.getNode(ISD::TRUNCATE, dl, RType, TopHalf);
+
+    assert(RType.getSizeInBits() == TopHalf.getValueSizeInBits() &&
+           "Unexpected result type for S/UMULO legalization");
+
     Results.push_back(BottomHalf);
     Results.push_back(TopHalf);
     break;
diff --git a/llvm/test/CodeGen/MSP430/umulo-16.ll b/llvm/test/CodeGen/MSP430/umulo-16.ll
new file mode 100644
index 0000000..bd42137
--- /dev/null
+++ b/llvm/test/CodeGen/MSP430/umulo-16.ll
@@ -0,0 +1,32 @@
+; RUN: llc < %s -march=msp430 | FileCheck %s
+target datalayout = "e-m:e-p:16:16-i32:16:32-a:16-n8:16"
+target triple = "msp430"
+
+define void @foo(i16 %arg) unnamed_addr {
+entry-block:
+  br i1 undef, label %bb2, label %bb3
+
+bb2:                                              ; preds = %entry-block
+  unreachable
+
+bb3:                                              ; preds = %entry-block
+  %0 = call { i16, i1 } @llvm.umul.with.overflow.i16(i16 undef, i16 %arg)
+; CHECK: call
+  %1 = extractvalue { i16, i1 } %0, 1
+  %2 = call i1 @llvm.expect.i1(i1 %1, i1 false)
+  br i1 %2, label %panic, label %bb5
+
+bb5:                                              ; preds = %bb3
+  unreachable
+
+panic:                                            ; preds = %bb3
+  unreachable
+}
+
+; Function Attrs: nounwind readnone
+declare i1 @llvm.expect.i1(i1, i1) #0
+
+; Function Attrs: nounwind readnone
+declare { i16, i1 } @llvm.umul.with.overflow.i16(i16, i16) #0
+
+attributes #0 = { nounwind readnone }
-- 
2.7.4