[PATCH] D158304: [RISCV] Fix a UBSAN failure for passing INT64_MIN to std::abs.

[Craig Topper via Phabricator via llvm-commits]

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clang recently started checking for INT64_MIN being passed to 64-bit std::abs.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D158304

Files:
  llvm/lib/Target/RISCV/RISCVISelLowering.cpp


Index: llvm/lib/Target/RISCV/RISCVISelLowering.cpp
===================================================================
--- llvm/lib/Target/RISCV/RISCVISelLowering.cpp
+++ llvm/lib/Target/RISCV/RISCVISelLowering.cpp
@@ -3232,12 +3232,13 @@
     bool Negate = false;
     int64_t SplatStepVal = StepNumerator;
     unsigned StepOpcode = ISD::MUL;
-    if (StepNumerator != 1) {
-      if (isPowerOf2_64(std::abs(StepNumerator))) {
-        Negate = StepNumerator < 0;
-        StepOpcode = ISD::SHL;
-        SplatStepVal = Log2_64(std::abs(StepNumerator));
-      }
+    // Exclude INT64_MIN to avoid passing it to std::abs. We won't optimize it
+    // anyway as the shift of 63 won't fit in uimm5.
+    if (StepNumerator != 1 && StepNumerator != INT64_MIN &&
+        isPowerOf2_64(std::abs(StepNumerator))) {
+      Negate = StepNumerator < 0;
+      StepOpcode = ISD::SHL;
+      SplatStepVal = Log2_64(std::abs(StepNumerator));
     }
 
     // Only emit VIDs with suitably-small steps/addends. We use imm5 is a


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