[PATCH] D122967: [InstCombine] fold more constant divisor to select-of-constants divisor

[Chenbing.Zheng via Phabricator via llvm-commits]

Chenbing.Zheng updated this revision to Diff 421137.
Chenbing.Zheng added a comment.

address comments


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122967/new/

https://reviews.llvm.org/D122967

Files:
  llvm/lib/Transforms/InstCombine/InstCombineInternal.h
  llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
  llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
  llvm/test/Transforms/InstCombine/div.ll


Index: llvm/test/Transforms/InstCombine/div.ll
===================================================================
--- llvm/test/Transforms/InstCombine/div.ll
+++ llvm/test/Transforms/InstCombine/div.ll
@@ -1098,13 +1098,11 @@
   ret i32 %r
 }
 
-; TODO: sdiv should still be replaced by select.
-
 define i32 @sdiv_constant_dividend_select_of_constants_divisor_use(i1 %b) {
 ; CHECK-LABEL: @sdiv_constant_dividend_select_of_constants_divisor_use(
 ; CHECK-NEXT:    [[S:%.*]] = select i1 [[B:%.*]], i32 12, i32 -3
 ; CHECK-NEXT:    call void @use(i32 [[S]])
-; CHECK-NEXT:    [[R:%.*]] = sdiv i32 42, [[S]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i32 3, i32 -14
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %s = select i1 %b, i32 12, i32 -3
@@ -1204,13 +1202,11 @@
   ret i32 %r
 }
 
-; TODO: udiv should still be replaced by select.
-
 define i32 @udiv_constant_dividend_select_of_constants_divisor_use(i1 %b) {
 ; CHECK-LABEL: @udiv_constant_dividend_select_of_constants_divisor_use(
 ; CHECK-NEXT:    [[S:%.*]] = select i1 [[B:%.*]], i32 12, i32 -3
 ; CHECK-NEXT:    call void @use(i32 [[S]])
-; CHECK-NEXT:    [[R:%.*]] = udiv i32 42, [[S]]
+; CHECK-NEXT:    [[R:%.*]] = select i1 [[B]], i32 3, i32 0
 ; CHECK-NEXT:    ret i32 [[R]]
 ;
   %s = select i1 %b, i32 12, i32 -3
Index: llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ llvm/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1037,10 +1037,10 @@
   return NewBO;
 }
 
-Instruction *InstCombinerImpl::FoldOpIntoSelect(Instruction &Op,
-                                                SelectInst *SI) {
-  // Don't modify shared select instructions.
-  if (!SI->hasOneUse())
+Instruction *InstCombinerImpl::FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
+                                                bool FoldWithMultiUse) {
+  // Don't modify shared select instructions unless set FoldWithMultiUse
+  if (!SI->hasOneUse() && !FoldWithMultiUse)
     return nullptr;
 
   Value *TV = SI->getTrueValue();
Index: llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineMulDivRem.cpp
@@ -772,7 +772,8 @@
   // TODO: Adapt simplifyDivRemOfSelectWithZeroOp to allow this and other folds.
   if (match(Op0, m_ImmConstant()) &&
       match(Op1, m_Select(m_Value(), m_ImmConstant(), m_ImmConstant()))) {
-    if (Instruction *R = FoldOpIntoSelect(I, cast<SelectInst>(Op1)))
+    if (Instruction *R = FoldOpIntoSelect(I, cast<SelectInst>(Op1),
+                                          /*FoldWithMultiUse*/ true))
       return R;
   }
 
Index: llvm/lib/Transforms/InstCombine/InstCombineInternal.h
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineInternal.h
+++ llvm/lib/Transforms/InstCombine/InstCombineInternal.h
@@ -622,7 +622,8 @@
   /// other operand, try to fold the binary operator into the select arguments.
   /// This also works for Cast instructions, which obviously do not have a
   /// second operand.
-  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI);
+  Instruction *FoldOpIntoSelect(Instruction &Op, SelectInst *SI,
+                                bool FoldWithMultiUse = false);
 
   /// This is a convenience wrapper function for the above two functions.
   Instruction *foldBinOpIntoSelectOrPhi(BinaryOperator &I);


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