[llvm] ca51529 - [SystemZ] Extend combineGET_CCMASK() to handle a truncated SELECT_CCMASK.

[Jonas Paulsson via llvm-commits]

Author: Jonas Paulsson
Date: 2022-11-23T09:53:07-05:00
New Revision: ca515294879652a46c0e76aaa66f8e415e308b8d

URL: https://github.com/llvm/llvm-project/commit/ca515294879652a46c0e76aaa66f8e415e308b8d
DIFF: https://github.com/llvm/llvm-project/commit/ca515294879652a46c0e76aaa66f8e415e308b8d.diff

LOG: [SystemZ]  Extend combineGET_CCMASK() to handle a truncated SELECT_CCMASK.

In cases where the SELECT_CCMASK has an additional user of the carry, a
truncated SELECT_CCMASK may result as the input to the GET_CCMASK, which need
to be recognized.

Fixes https://github.com/llvm/llvm-project/issues/59054

Reviewed By: Ulrich Weigand

Differential Revision: https://reviews.llvm.org/D138324

Added: 
    llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll

Modified: 
    llvm/lib/Target/SystemZ/SystemZISelLowering.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index 95d87197b0f4d..01f47e63ad92c 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -7038,6 +7038,8 @@ SDValue SystemZTargetLowering::combineGET_CCMASK(
   int CCMaskVal = CCMask->getZExtValue();
 
   SDValue Select = N->getOperand(0);
+  if (Select->getOpcode() == ISD::TRUNCATE)
+    Select = Select->getOperand(0);
   if (Select->getOpcode() != SystemZISD::SELECT_CCMASK)
     return SDValue();
 
@@ -7052,9 +7054,9 @@ SDValue SystemZTargetLowering::combineGET_CCMASK(
   auto *FalseVal = dyn_cast<ConstantSDNode>(Select->getOperand(1));
   if (!TrueVal || !FalseVal)
     return SDValue();
-  if (TrueVal->getZExtValue() != 0 && FalseVal->getZExtValue() == 0)
+  if (TrueVal->getZExtValue() == 1 && FalseVal->getZExtValue() == 0)
     ;
-  else if (TrueVal->getZExtValue() == 0 && FalseVal->getZExtValue() != 0)
+  else if (TrueVal->getZExtValue() == 0 && FalseVal->getZExtValue() == 1)
     SelectCCMaskVal ^= SelectCCValidVal;
   else
     return SDValue();

diff  --git a/llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll b/llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll
new file mode 100644
index 0000000000000..6d57dcfefd423
--- /dev/null
+++ b/llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll
@@ -0,0 +1,23 @@
+; RUN: llc < %s -mtriple=s390x-linux-gnu -start-after=codegenprepare | FileCheck %s
+;
+; Test that compilation succeeds with multiple users of the carry resulting
+; in a truncation of the SELECT_CCMASK used by GET_CCMASK.
+
+define void @fun() {
+; CHECK-LABEL: fun:
+bb:
+  %0 = call { i64, i1 } @llvm.uadd.with.overflow.i64(i64 poison, i64 poison)
+  %ov = extractvalue { i64, i1 } %0, 1
+  %i2 = sext i1 %ov to i64
+  %i3 = select i1 %ov, i64 9223372036854775807, i64 -1
+  %i4 = sub nsw i64 %i3, %i2
+  %i5 = and i64 %i4, %i2
+  %i6 = icmp slt i64 %i5, 0
+  %i7 = xor i1 %ov, true
+  %i8 = select i1 %i6, i1 %i7, i1 false
+  %i9 = sext i1 %i8 to i16
+  store i16 %i9, ptr poison, align 2
+  unreachable
+}
+
+declare { i64, i1 } @llvm.uadd.with.overflow.i64(i64, i64)