[PATCH] D15249: [InstCombine] Call getCmpPredicateForMinMax only with a valid SPF

[Sanjoy Das via llvm-commits]

sanjoy created this revision.
sanjoy added a reviewer: majnemer.
sanjoy added a subscriber: llvm-commits.

There are `SelectPatternFlavor`s that don't represent min or max idioms,
and we should not be passing those to `getCmpPredicateForMinMax`.

Fixes PR25745.

http://reviews.llvm.org/D15249

Files:
  include/llvm/Analysis/ValueTracking.h
  lib/Transforms/InstCombine/InstCombineSelect.cpp
  test/Transforms/InstCombine/pr25745.ll

Index: test/Transforms/InstCombine/pr25745.ll
===================================================================
--- /dev/null
+++ test/Transforms/InstCombine/pr25745.ll
@@ -0,0 +1,20 @@
+; RUN: opt -S -instcombine < %s | FileCheck %s
+
+; Checking for a crash
+
+declare void @use.i1(i1 %val)
+declare void @use.i64(i64 %val)
+
+define i64 @f(i32 %x) {
+; CHECK-LABEL: @f(
+ entry:
+  %x.wide = sext i32 %x to i64
+  %minus.x = sub i32 0, %x
+  %minus.x.wide = sext i32 %minus.x to i64
+  %c = icmp slt i32 %x, 0
+  %val = select i1 %c, i64 %x.wide, i64 %minus.x.wide
+  call void @use.i1(i1 %c)
+  call void @use.i64(i64 %x.wide)
+  ret i64 %val
+; CHECK: ret i64 %val
+}
Index: lib/Transforms/InstCombine/InstCombineSelect.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -1070,7 +1070,7 @@
     SelectPatternResult SPR = matchSelectPattern(&SI, LHS, RHS, &CastOp);
     auto SPF = SPR.Flavor;
 
-    if (SPF) {
+    if (SelectPatternResult::isMinOrMax(SPF)) {
       // Canonicalize so that type casts are outside select patterns.
       if (LHS->getType()->getPrimitiveSizeInBits() !=
           SI.getType()->getPrimitiveSizeInBits()) {
@@ -1091,11 +1091,15 @@
                                            SI.getType());
         return ReplaceInstUsesWith(SI, NewSI);
       }
+    }
 
+    if (SPF) {
       // MAX(MAX(a, b), a) -> MAX(a, b)
       // MIN(MIN(a, b), a) -> MIN(a, b)
       // MAX(MIN(a, b), a) -> a
       // MIN(MAX(a, b), a) -> a
+      // ABS(ABS(a)) -> ABS(a)
+      // NABS(NABS(a)) -> NABS(a)
       if (SelectPatternFlavor SPF2 = matchSelectPattern(LHS, LHS2, RHS2).Flavor)
         if (Instruction *R = FoldSPFofSPF(cast<Instruction>(LHS),SPF2,LHS2,RHS2,
                                           SI, SPF, RHS))
Index: include/llvm/Analysis/ValueTracking.h
===================================================================
--- include/llvm/Analysis/ValueTracking.h
+++ include/llvm/Analysis/ValueTracking.h
@@ -412,6 +412,11 @@
     bool Ordered;               /// When implementing this min/max pattern as
                                 /// fcmp; select, does the fcmp have to be
                                 /// ordered?
+
+    /// \brief Return true if \p SPF is a min or a max pattern.
+    static bool isMinOrMax(SelectPatternFlavor SPF) {
+      return !(SPF == SPF_UNKNOWN || SPF == SPF_ABS || SPF == SPF_NABS);
+    }
   };
   /// Pattern match integer [SU]MIN, [SU]MAX and ABS idioms, returning the kind
   /// and providing the out parameter results if we successfully match.


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