[llvm-commits] [llvm] r172117 - in /llvm/trunk: lib/Transforms/InstCombine/InstCombineCasts.cpp test/Transforms/InstCombine/fpcast.ll

[Owen Anderson]

Author: resistor
Date: Thu Jan 10 16:06:52 2013
New Revision: 172117

URL: http://llvm.org/viewvc/llvm-project?rev=172117&view=rev
Log:
Teach InstCombine to hoist FABS and FNEG through FPTRUNC instructions.  The application of these operations commutes with the truncation, so we should prefer to do them in the smallest size we can, to save register space, use smaller constant pool entries, etc.

Modified:
    llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
    llvm/trunk/test/Transforms/InstCombine/fpcast.ll

Modified: llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp?rev=172117&r1=172116&r2=172117&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp (original)
+++ llvm/trunk/lib/Transforms/InstCombine/InstCombineCasts.cpp Thu Jan 10 16:06:52 2013
@@ -1204,8 +1204,34 @@
       }
       break;  
     }
+
+    // (fptrunc (fneg x)) -> (fneg (fptrunc x))
+    if (BinaryOperator::isFNeg(OpI)) {
+      Value *InnerTrunc = Builder->CreateFPTrunc(OpI->getOperand(1),
+                                                 CI.getType());
+      return BinaryOperator::CreateFNeg(InnerTrunc);
+    }
   }
-  
+
+  IntrinsicInst *II = dyn_cast<IntrinsicInst>(CI.getOperand(0));
+  if (II) {
+    switch (II->getIntrinsicID()) {
+      default: break;
+      case Intrinsic::fabs: {
+        // (fptrunc (fabs x)) -> (fabs (fptrunc x))
+        Value *InnerTrunc = Builder->CreateFPTrunc(II->getArgOperand(0),
+                                                   CI.getType());
+        Type *IntrinsicType[] = { CI.getType() };
+        Function *Overload =
+          Intrinsic::getDeclaration(CI.getParent()->getParent()->getParent(),
+                                    II->getIntrinsicID(), IntrinsicType);
+
+        Value *Args[] = { InnerTrunc };
+        return CallInst::Create(Overload, Args, II->getName());
+      }
+    }
+  }
+
   // Fold (fptrunc (sqrt (fpext x))) -> (sqrtf x)
   CallInst *Call = dyn_cast<CallInst>(CI.getOperand(0));
   if (Call && Call->getCalledFunction() && TLI->has(LibFunc::sqrtf) &&

Modified: llvm/trunk/test/Transforms/InstCombine/fpcast.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/InstCombine/fpcast.ll?rev=172117&r1=172116&r2=172117&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/InstCombine/fpcast.ll (original)
+++ llvm/trunk/test/Transforms/InstCombine/fpcast.ll Thu Jan 10 16:06:52 2013
@@ -13,3 +13,22 @@
 ; CHECK: ret i8 -1
 }
 
+; CHECK: test3
+define half @test3(float %a) {
+; CHECK: fptrunc
+; CHECK: llvm.fabs.f16
+  %b = call float @llvm.fabs.f32(float %a)
+  %c = fptrunc float %b to half
+  ret half %c
+}
+
+; CHECK: test4
+define half @test4(float %a) {
+; CHECK: fptrunc
+; CHECK: fsub
+  %b = fsub float -0.0, %a
+  %c = fptrunc float %b to half
+  ret half %c
+}
+
+declare float @llvm.fabs.f32(float) nounwind readonly