File backport-llvm-r233541 of Package llvm

------------------------------------------------------------------------
r233541 | uweigand | 2015-03-30 15:46:59 +0200 (Mon, 30 Mar 2015) | 13 lines

[SystemZ] Fix LLVM crash on unoptimized code

Compiling the following function with -O0 would crash, since LLVM would
hit an assertion in getTestUnderMaskCond:

  int test(unsigned long x)
  {
    return x >= 0 && x <= 15;
  }

Fixed by detecting the case in the caller of getTestUnderMaskCond.


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Index: lib/Target/SystemZ/SystemZISelLowering.cpp
===================================================================
--- lib/Target/SystemZ/SystemZISelLowering.cpp.orig
+++ lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -1529,6 +1529,8 @@ static void adjustForTestUnderMask(Selec
     MaskVal = -(CmpVal & -CmpVal);
     NewC.ICmpType = SystemZICMP::UnsignedOnly;
   }
+  if (!MaskVal)
+    return;
 
   // Check whether the combination of mask, comparison value and comparison
   // type are suitable.
Index: test/CodeGen/SystemZ/int-cmp-50.ll
===================================================================
--- /dev/null
+++ test/CodeGen/SystemZ/int-cmp-50.ll
@@ -0,0 +1,30 @@
+; Verify that we do not crash on always-true conditions
+;
+; RUN: llc < %s -mtriple=s390x-linux-gnu -mcpu=z10 -O0
+;
+; This test was compiled using clang -O0 from the following source code:
+;
+; int test(unsigned long x)
+; {
+;   return x >= 0 && x <= 15;
+; }
+
+define signext i32 @test(i64 %x) {
+entry:
+  %x.addr = alloca i64, align 8
+  store i64 %x, i64* %x.addr, align 8
+  %0 = load i64 *%x.addr, align 8
+  %cmp = icmp uge i64 %0, 0
+  br i1 %cmp, label %land.rhs, label %land.end
+
+land.rhs:                                         ; preds = %entry
+  %1 = load i64 *%x.addr, align 8
+  %cmp1 = icmp ule i64 %1, 15
+  br label %land.end
+
+land.end:                                         ; preds = %land.rhs, %entry
+  %2 = phi i1 [ false, %entry ], [ %cmp1, %land.rhs ]
+  %land.ext = zext i1 %2 to i32
+  ret i32 %land.ext
+}
+