[PATCH] D73647: [InstCombine] Support non-splat vectors in icmp eq + add/sub fold

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: spatel, lebedev.ri, xbolva00.
Herald added subscribers: llvm-commits, hiraditya.
Herald added a project: LLVM.

For the `icmp eq (add X, C1), C2 => icmp eq X, C2-C1` and `icmp eq (sub C1, X), C2 => icmp eq X, C1-C2` folds, this allows `C1` to be non-splat and contain undefs. `C2` is still splat, due to the structure of the code.

This is to address the remaining part of the regression in D73411 <https://reviews.llvm.org/D73411>, where demanded element analysis replaces some elements with undef.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D73647

Files:
  llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
  llvm/test/Transforms/InstCombine/icmp-add.ll
  llvm/test/Transforms/InstCombine/icmp-sub.ll


Index: llvm/test/Transforms/InstCombine/icmp-sub.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-sub.ll
+++ llvm/test/Transforms/InstCombine/icmp-sub.ll
@@ -146,8 +146,7 @@
 
 define <2 x i1> @icmp_eq_sub_undef(<2 x i32> %a) {
 ; CHECK-LABEL: @icmp_eq_sub_undef(
-; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i32> <i32 15, i32 undef>, [[A:%.*]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[SUB]], <i32 10, i32 10>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[A:%.*]], <i32 5, i32 undef>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %sub = sub <2 x i32> <i32 15, i32 undef>, %a
@@ -157,8 +156,7 @@
 
 define <2 x i1> @icmp_eq_sub_non_splat(<2 x i32> %a) {
 ; CHECK-LABEL: @icmp_eq_sub_non_splat(
-; CHECK-NEXT:    [[SUB:%.*]] = sub <2 x i32> <i32 15, i32 16>, [[A:%.*]]
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[SUB]], <i32 10, i32 10>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[A:%.*]], <i32 5, i32 6>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %sub = sub <2 x i32> <i32 15, i32 16>, %a
Index: llvm/test/Transforms/InstCombine/icmp-add.ll
===================================================================
--- llvm/test/Transforms/InstCombine/icmp-add.ll
+++ llvm/test/Transforms/InstCombine/icmp-add.ll
@@ -624,8 +624,7 @@
 
 define <2 x i1> @icmp_eq_add_undef(<2 x i32> %a) {
 ; CHECK-LABEL: @icmp_eq_add_undef(
-; CHECK-NEXT:    [[ADD:%.*]] = add <2 x i32> [[A:%.*]], <i32 5, i32 undef>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[ADD]], <i32 10, i32 10>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[A:%.*]], <i32 5, i32 undef>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %add = add <2 x i32> %a, <i32 5, i32 undef>
@@ -635,8 +634,7 @@
 
 define <2 x i1> @icmp_eq_add_non_splat(<2 x i32> %a) {
 ; CHECK-LABEL: @icmp_eq_add_non_splat(
-; CHECK-NEXT:    [[ADD:%.*]] = add <2 x i32> [[A:%.*]], <i32 5, i32 6>
-; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[ADD]], <i32 10, i32 10>
+; CHECK-NEXT:    [[CMP:%.*]] = icmp eq <2 x i32> [[A:%.*]], <i32 5, i32 4>
 ; CHECK-NEXT:    ret <2 x i1> [[CMP]]
 ;
   %add = add <2 x i32> %a, <i32 5, i32 6>
Index: llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
===================================================================
--- llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
+++ llvm/lib/Transforms/InstCombine/InstCombineCompares.cpp
@@ -2928,12 +2928,9 @@
     break;
   case Instruction::Add: {
     // Replace ((add A, B) != C) with (A != C-B) if B & C are constants.
-    const APInt *BOC;
-    if (match(BOp1, m_APInt(BOC))) {
-      if (BO->hasOneUse()) {
-        Constant *SubC = ConstantExpr::getSub(RHS, cast<Constant>(BOp1));
-        return new ICmpInst(Pred, BOp0, SubC);
-      }
+    if (Constant *BOC = dyn_cast<Constant>(BOp1)) {
+      if (BO->hasOneUse())
+        return new ICmpInst(Pred, BOp0, ConstantExpr::getSub(RHS, BOC));
     } else if (C.isNullValue()) {
       // Replace ((add A, B) != 0) with (A != -B) if A or B is
       // efficiently invertible, or if the add has just this one use.
@@ -2963,11 +2960,9 @@
     break;
   case Instruction::Sub:
     if (BO->hasOneUse()) {
-      const APInt *BOC;
-      if (match(BOp0, m_APInt(BOC))) {
+      if (Constant *BOC = dyn_cast<Constant>(BOp0)) {
         // Replace ((sub BOC, B) != C) with (B != BOC-C).
-        Constant *SubC = ConstantExpr::getSub(cast<Constant>(BOp0), RHS);
-        return new ICmpInst(Pred, BOp1, SubC);
+        return new ICmpInst(Pred, BOp1, ConstantExpr::getSub(BOC, RHS));
       } else if (C.isNullValue()) {
         // Replace ((sub A, B) != 0) with (A != B).
         return new ICmpInst(Pred, BOp0, BOp1);


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