[PATCH] D138324: [SystemZ] Make sure that combineGET_CCMASK() can handle a truncated SELECT_CCMASK.

[Jonas Paulsson via Phabricator via llvm-commits]

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In cases where the SELECT_CCMASK has an additional user of the the carry a truncated SELECT_CCMASK may result as the input to a GET_CCMASK. This patch adds capability to combineGET_CCMASK() to recognize and handle these cases.

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


https://reviews.llvm.org/D138324

Files:
  llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
  llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll


Index: llvm/test/CodeGen/SystemZ/int-uadd-multiple-carry-users.ll
===================================================================
--- /dev/null
+++ 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)
Index: llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
===================================================================
--- llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -7038,6 +7038,17 @@
   int CCMaskVal = CCMask->getZExtValue();
 
   SDValue Select = N->getOperand(0);
+  if (Select->getOpcode() == ISD::TRUNCATE) {
+    Select = Select->getOperand(0);
+    if (Select->getOpcode() == SystemZISD::SELECT_CCMASK) {
+      auto *TrueOp = dyn_cast<ConstantSDNode>(Select->getOperand(0));
+      auto *FalseOp = dyn_cast<ConstantSDNode>(Select->getOperand(1));
+      if (!TrueOp || !FalseOp ||
+          (TrueOp->getZExtValue() != 0 && TrueOp->getZExtValue() != 1) ||
+          (FalseOp->getZExtValue() != 0 && FalseOp->getZExtValue() != 1))
+        return SDValue();
+    }
+  }
   if (Select->getOpcode() != SystemZISD::SELECT_CCMASK)
     return SDValue();
 


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