[PATCH] [InstCombine] Canonicalize min/max expressions correctly.

[David Majnemer]

REPOSITORY
  rL LLVM

================
Comment at: lib/Transforms/InstCombine/InstCombineSelect.cpp:1169-1176
@@ +1168,10 @@
+          SI.getType()->getPrimitiveSizeInBits()) {
+        CmpInst::Predicate Pred;
+        switch (SPF) {
+        case SPF_SMIN: Pred = CmpInst::ICMP_SLT; break;
+        case SPF_SMAX: Pred = CmpInst::ICMP_SGT; break;
+        case SPF_UMIN: Pred = CmpInst::ICMP_ULT; break;
+        case SPF_UMAX: Pred = CmpInst::ICMP_UGT; break;
+        default: llvm_unreachable("Unknown SPF type!");
+        }
+        return CastInst::Create(CastOp,
----------------
This looks the same as `getICmpPredicateForMinMax`.

================
Comment at: lib/Transforms/InstCombine/InstCombineSelect.cpp:1177-1182
@@ +1176,8 @@
+        }
+        return CastInst::Create(CastOp,
+                                SelectInst::Create(
+                                  CmpInst::Create(Instruction::ICmp, Pred,
+                                                  LHS, RHS, "", &SI),
+                                  LHS, RHS, "", &SI),
+                                SI.getType());
+      }
----------------
I'd expect you to use the IRBuilder to construct each instruction up until the last which I'd expect you'd feed into `ReplaceInstUsesWith`.

http://reviews.llvm.org/D9749

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