Revert "Revert "InstCombine: Improvement to check if signed addition overflows.""

[oota-llvm.git] / lib / Transforms / InstCombine / InstCombineSelect.cpp

diff --git a/lib/Transforms/InstCombine/InstCombineSelect.cpp b/lib/Transforms/InstCombine/InstCombineSelect.cpp
index 795e645840cbec1be1d3524bcf7485941e3a163b..9a41e4b9406ad5a6563a2f16d7e9f314bc87ec2a 100644 (file)
--- a/lib/Transforms/InstCombine/InstCombineSelect.cpp
+++ b/lib/Transforms/InstCombine/InstCombineSelect.cpp
@@ -651,11 +651,35 @@ Instruction *InstCombiner::FoldSPFofSPF(Instruction *Inner,
       return ReplaceInstUsesWith(Outer, C);
   }
 
-  // TODO: MIN(MIN(A, 23), 97)
+  if (SPF1 == SPF2) {
+    if (ConstantInt *CB = dyn_cast<ConstantInt>(B)) {
+      if (ConstantInt *CC = dyn_cast<ConstantInt>(C)) {
+        APInt ACB = CB->getValue();
+        APInt ACC = CC->getValue();
+
+        // MIN(MIN(A, 23), 97) -> MIN(A, 23)
+        // MAX(MAX(A, 97), 23) -> MAX(A, 97)
+        if ((SPF1 == SPF_UMIN && ACB.ule(ACC)) ||
+            (SPF1 == SPF_SMIN && ACB.sle(ACC)) ||
+            (SPF1 == SPF_UMAX && ACB.uge(ACC)) ||
+            (SPF1 == SPF_SMAX && ACB.sge(ACC)))
+          return ReplaceInstUsesWith(Outer, Inner);
+
+        // MIN(MIN(A, 97), 23) -> MIN(A, 23)
+        // MAX(MAX(A, 23), 97) -> MAX(A, 97)
+        if ((SPF1 == SPF_UMIN && ACB.ugt(ACC)) ||
+            (SPF1 == SPF_SMIN && ACB.sgt(ACC)) ||
+            (SPF1 == SPF_UMAX && ACB.ult(ACC)) ||
+            (SPF1 == SPF_SMAX && ACB.slt(ACC))) {
+          Outer.replaceUsesOfWith(Inner, A);
+          return &Outer;
+        }
+      }
+    }
+  }
   return nullptr;
 }
 
-
 /// foldSelectICmpAnd - If one of the constants is zero (we know they can't
 /// both be) and we have an icmp instruction with zero, and we have an 'and'
 /// with the non-constant value and a power of two we can turn the select