[PATCH] D48447: Fix invariant fdiv hoisting in LICM

[Stanislav Mekhanoshin via Phabricator via llvm-commits]

This revision was automatically updated to reflect the committed changes.
Closed by commit rL335411: Fix invariant fdiv hoisting in LICM (authored by rampitec, committed by ).

Changed prior to commit:
  https://reviews.llvm.org/D48447?vs=152348&id=152584#toc

Repository:
  rL LLVM

https://reviews.llvm.org/D48447

Files:
  llvm/trunk/lib/Transforms/Scalar/LICM.cpp
  llvm/trunk/test/Transforms/LICM/hoist-fast-fdiv.ll


Index: llvm/trunk/lib/Transforms/Scalar/LICM.cpp
===================================================================
--- llvm/trunk/lib/Transforms/Scalar/LICM.cpp
+++ llvm/trunk/lib/Transforms/Scalar/LICM.cpp
@@ -477,6 +477,20 @@
         continue;
       }
 
+      // Try hoisting the instruction out to the preheader.  We can only do
+      // this if all of the operands of the instruction are loop invariant and
+      // if it is safe to hoist the instruction.
+      //
+      if (CurLoop->hasLoopInvariantOperands(&I) &&
+          canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) &&
+          (IsMustExecute ||
+           isSafeToExecuteUnconditionally(
+               I, DT, CurLoop, SafetyInfo, ORE,
+               CurLoop->getLoopPreheader()->getTerminator()))) {
+        Changed |= hoist(I, DT, CurLoop, SafetyInfo, ORE);
+        continue;
+      }
+
       // Attempt to remove floating point division out of the loop by
       // converting it to a reciprocal multiplication.
       if (I.getOpcode() == Instruction::FDiv &&
@@ -500,20 +514,6 @@
         continue;
       }
 
-      // Try hoisting the instruction out to the preheader.  We can only do
-      // this if all of the operands of the instruction are loop invariant and
-      // if it is safe to hoist the instruction.
-      //
-      if (CurLoop->hasLoopInvariantOperands(&I) &&
-          canSinkOrHoistInst(I, AA, DT, CurLoop, CurAST, SafetyInfo, ORE) &&
-          (IsMustExecute ||
-           isSafeToExecuteUnconditionally(
-               I, DT, CurLoop, SafetyInfo, ORE,
-               CurLoop->getLoopPreheader()->getTerminator()))) {
-        Changed |= hoist(I, DT, CurLoop, SafetyInfo, ORE);
-        continue;
-      }
-
       if (IsMustExecute)
         IsMustExecute = isGuaranteedToTransferExecutionToSuccessor(&I);
     }
Index: llvm/trunk/test/Transforms/LICM/hoist-fast-fdiv.ll
===================================================================
--- llvm/trunk/test/Transforms/LICM/hoist-fast-fdiv.ll
+++ llvm/trunk/test/Transforms/LICM/hoist-fast-fdiv.ll
@@ -1,9 +1,9 @@
 ; RUN: opt -licm -S < %s | FileCheck %s
 
 ; Function Attrs: noinline norecurse nounwind readnone ssp uwtable
-define zeroext i1 @f(double %v) #0 {
+define zeroext i1 @invariant_denom(double %v) #0 {
 entry:
-; CHECK-LABEL: @f(
+; CHECK-LABEL: @invariant_denom(
 ; CHECK-NEXT: entry:
 ; CHECK-NEXT: fdiv fast double 1.000000e+00, %v
   br label %loop
@@ -32,3 +32,29 @@
   ret i1 %v16
 }
 
+define void @invariant_fdiv(float* %out, float %arg) {
+; CHECK-LABEL: @invariant_fdiv(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: %div = fdiv fast float 4.000000e+00, %arg
+; CHECK-NEXT: fmul fast float %div, 0x41F0000000000000
+entry:
+  br label %loop
+
+loop:                                              ; preds = %loop, %entry
+  %ind = phi i32 [ 0, %entry ], [ %inc, %loop ]
+
+; CHECK-LABEL: loop:
+; CHECK: getelementptr
+; CHECK-NOT: fdiv
+; CHECK-NOT: fmul
+  %div = fdiv fast float 4.000000e+00, %arg
+  %mul = fmul fast float %div, 0x41F0000000000000
+  %gep = getelementptr inbounds float, float* %out, i32 %ind
+  store float %mul, float* %gep, align 4
+  %inc = add nuw nsw i32 %ind, 1
+  %cond = icmp eq i32 %inc, 1024
+  br i1 %cond, label %exit, label %loop
+
+exit:                                              ; preds = %loop
+  ret void
+}


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