[PATCH] D85946: [InstSimplify] Inline vector constants

[Arthur Eubanks via Phabricator via llvm-commits]

aeubanks created this revision.
Herald added subscribers: llvm-commits, hiraditya.
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InstSimplify should do all transformations that ConstProp does, but
one thing that ConstProp does that InstSimplify wouldn't is inline
vector instructions that are constants, e.g. into a ret.

Previously vector instructions wouldn't be inlined in InstSimplify
because llvm::SimplifyInstruction() would return nullptr for specific
instructions, such as vector instructions that were actually constants,
if it couldn't simplify them. Rather, it should fall back to
ConstantFoldInstruction(), which converts an instruction to a constant
when possible.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D85946

Files:
  llvm/lib/Analysis/InstructionSimplify.cpp
  llvm/test/Analysis/ConstantFolding/vscale-shufflevector.ll
  llvm/test/Transforms/InstSimplify/select.ll


Index: llvm/test/Transforms/InstSimplify/select.ll
===================================================================
--- llvm/test/Transforms/InstSimplify/select.ll
+++ llvm/test/Transforms/InstSimplify/select.ll
@@ -890,8 +890,7 @@
 ; Negative tests. Don't fold if the non-undef operand is a constexpr.
 define i32 @all_constant_false_undef_true_constexpr() {
 ; CHECK-LABEL: @all_constant_false_undef_true_constexpr(
-; CHECK-NEXT:    [[S:%.*]] = select i1 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i32), i32 undef
-; CHECK-NEXT:    ret i32 [[S]]
+; CHECK-NEXT:    ret i32 select (i1 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i32), i32 undef)
 ;
   %s = select i1 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i1), i32 ptrtoint (i32 ()* @all_constant_false_undef_true_constexpr to i32), i32 undef
   ret i32 %s
@@ -899,8 +898,7 @@
 
 define i32 @all_constant_true_undef_false_constexpr() {
 ; CHECK-LABEL: @all_constant_true_undef_false_constexpr(
-; CHECK-NEXT:    [[S:%.*]] = select i1 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i32)
-; CHECK-NEXT:    ret i32 [[S]]
+; CHECK-NEXT:    ret i32 select (i1 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i32))
 ;
   %s = select i1 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i1), i32 undef, i32 ptrtoint (i32 ()* @all_constant_true_undef_false_constexpr to i32)
   ret i32 %s
@@ -909,8 +907,7 @@
 ; Negative tests. Don't fold if the non-undef operand is a vector containing a constexpr.
 define <2 x i32> @all_constant_false_undef_true_constexpr_vec() {
 ; CHECK-LABEL: @all_constant_false_undef_true_constexpr_vec(
-; CHECK-NEXT:    [[S:%.*]] = select i1 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
-; CHECK-NEXT:    ret <2 x i32> [[S]]
+; CHECK-NEXT:    ret <2 x i32> select (i1 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef)
 ;
   %s = select i1 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i1), <2 x i32> <i32 ptrtoint (<2 x i32> ()* @all_constant_false_undef_true_constexpr_vec to i32), i32 -1>, <2 x i32> undef
   ret <2 x i32> %s
@@ -918,8 +915,7 @@
 
 define <2 x i32> @all_constant_true_undef_false_constexpr_vec() {
 ; CHECK-LABEL: @all_constant_true_undef_false_constexpr_vec(
-; CHECK-NEXT:    [[S:%.*]] = select i1 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32> <i32 -1, i32 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i32)>
-; CHECK-NEXT:    ret <2 x i32> [[S]]
+; CHECK-NEXT:    ret <2 x i32> select (i1 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32> <i32 -1, i32 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i32)>)
 ;
   %s = select i1 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i1), <2 x i32> undef, <2 x i32><i32 -1, i32 ptrtoint (<2 x i32> ()* @all_constant_true_undef_false_constexpr_vec to i32)>
   ret <2 x i32> %s
Index: llvm/test/Analysis/ConstantFolding/vscale-shufflevector.ll
===================================================================
--- llvm/test/Analysis/ConstantFolding/vscale-shufflevector.ll
+++ llvm/test/Analysis/ConstantFolding/vscale-shufflevector.ll
@@ -15,9 +15,7 @@
 ; the compiler. It happens to be the case that this will be the result.
 
 ; CHECK-LABEL: define <vscale x 8 x i1> @vscale_version()
-; CHECK-NEXT: %splatter = insertelement <vscale x 8 x i1> undef, i1 true, i32 0
-; CHECK-NEXT: %foo = shufflevector <vscale x 8 x i1> %splatter, <vscale x 8 x i1> undef, <vscale x 8 x i32> zeroinitializer
-; CHECK-NEXT: ret <vscale x 8 x i1> %foo
+; CHECK-NEXT: ret <vscale x 8 x i1> shufflevector (<vscale x 8 x i1> insertelement (<vscale x 8 x i1> undef, i1 true, i32 0), <vscale x 8 x i1> undef, <vscale x 8 x i32> zeroinitializer)
 
 define <vscale x 8 x i1> @vscale_version() {
   %splatter = insertelement <vscale x 8 x i1> undef, i1 true, i32 0
Index: llvm/lib/Analysis/InstructionSimplify.cpp
===================================================================
--- llvm/lib/Analysis/InstructionSimplify.cpp
+++ llvm/lib/Analysis/InstructionSimplify.cpp
@@ -5595,11 +5595,10 @@
 Value *llvm::SimplifyInstruction(Instruction *I, const SimplifyQuery &SQ,
                                  OptimizationRemarkEmitter *ORE) {
   const SimplifyQuery Q = SQ.CxtI ? SQ : SQ.getWithInstruction(I);
-  Value *Result;
+  Value *Result = nullptr;
 
   switch (I->getOpcode()) {
   default:
-    Result = ConstantFoldInstruction(I, Q.DL, Q.TLI);
     break;
   case Instruction::FNeg:
     Result = SimplifyFNegInst(I->getOperand(0), I->getFastMathFlags(), Q);
@@ -5741,11 +5740,9 @@
     Result =
         SimplifyCastInst(I->getOpcode(), I->getOperand(0), I->getType(), Q);
     break;
-  case Instruction::Alloca:
-    // No simplifications for Alloca and it can't be constant folded.
-    Result = nullptr;
-    break;
   }
+  if (!Result)
+    Result = ConstantFoldInstruction(I, Q.DL, Q.TLI);
 
   /// If called on unreachable code, the above logic may report that the
   /// instruction simplified to itself.  Make life easier for users by


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