[PATCH] D57401: [DAGCombiner] fold add/sub with bool operand based on target's boolean contents

[Sanjay Patel via Phabricator via llvm-commits]

spatel updated this revision to Diff 184380.
spatel added a comment.

Patch updated:
The missing fold that was shown in the previous rev should be fixed here:
rL352680 <https://reviews.llvm.org/rL352680> (I added some extra tests to verify that was behaving as expected)

Interestingly, that actually caught my motivating cases for x86 and AArch in the earlier rev of this patch. So now we only show diffs for PPC tests, and those are all improvements. These tests also exist for x86, but there are no diffs there...I didn't step through all of those, but it looks like custom hacks to form LEA instructions mask any underlying changes.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57401/new/

https://reviews.llvm.org/D57401

Files:
  lib/CodeGen/SelectionDAG/DAGCombiner.cpp
  test/CodeGen/PowerPC/bool-math.ll
  test/CodeGen/PowerPC/signbit-shift.ll


Index: test/CodeGen/PowerPC/signbit-shift.ll
===================================================================
--- test/CodeGen/PowerPC/signbit-shift.ll
+++ test/CodeGen/PowerPC/signbit-shift.ll
@@ -69,9 +69,8 @@
 define i32 @add_sext_ifpos(i32 %x) {
 ; CHECK-LABEL: add_sext_ifpos:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    nor 3, 3, 3
-; CHECK-NEXT:    srawi 3, 3, 31
-; CHECK-NEXT:    addi 3, 3, 42
+; CHECK-NEXT:    srwi 3, 3, 31
+; CHECK-NEXT:    addi 3, 3, 41
 ; CHECK-NEXT:    blr
   %c = icmp sgt i32 %x, -1
   %e = sext i1 %c to i32
Index: test/CodeGen/PowerPC/bool-math.ll
===================================================================
--- test/CodeGen/PowerPC/bool-math.ll
+++ test/CodeGen/PowerPC/bool-math.ll
@@ -83,9 +83,8 @@
 define i32 @low_bit_select_constants_bigger_false_same_size_result(i32 %x) {
 ; CHECK-LABEL: low_bit_select_constants_bigger_false_same_size_result:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    not 3, 3
 ; CHECK-NEXT:    clrldi 3, 3, 63
-; CHECK-NEXT:    subfic 3, 3, 43
+; CHECK-NEXT:    ori 3, 3, 42
 ; CHECK-NEXT:    blr
   %a = and i32 %x, 1
   %c = icmp eq i32 %a, 0
@@ -96,9 +95,8 @@
 define i64 @low_bit_select_constants_bigger_false_wider_result(i32 %x) {
 ; CHECK-LABEL: low_bit_select_constants_bigger_false_wider_result:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    not 3, 3
 ; CHECK-NEXT:    clrldi 3, 3, 63
-; CHECK-NEXT:    subfic 3, 3, 27
+; CHECK-NEXT:    ori 3, 3, 26
 ; CHECK-NEXT:    blr
   %a = and i32 %x, 1
   %c = icmp eq i32 %a, 0
@@ -109,9 +107,8 @@
 define i16 @low_bit_select_constants_bigger_false_narrower_result(i32 %x) {
 ; CHECK-LABEL: low_bit_select_constants_bigger_false_narrower_result:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    nor 3, 3, 3
-; CHECK-NEXT:    clrlwi 3, 3, 31
-; CHECK-NEXT:    subfic 3, 3, 37
+; CHECK-NEXT:    clrldi 3, 3, 63
+; CHECK-NEXT:    ori 3, 3, 36
 ; CHECK-NEXT:    blr
   %a = and i32 %x, 1
   %c = icmp eq i32 %a, 0
Index: lib/CodeGen/SelectionDAG/DAGCombiner.cpp
===================================================================
--- lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -2288,10 +2288,12 @@
   if (SDValue V = foldAddSubMasked1(true, N0, N1, DAG, DL))
     return V;
 
-  // add (sext i1), X -> sub X, (zext i1)
+  // If the target's bool is represented as 0/1, prefer to make this 'sub 0/1'
+  // rather than 'add 0/-1' (the zext should get folded).
+  // add (sext i1 Y), X --> sub X, (zext i1 Y)
   if (N0.getOpcode() == ISD::SIGN_EXTEND &&
-      N0.getOperand(0).getValueType() == MVT::i1 &&
-      !TLI.isOperationLegal(ISD::SIGN_EXTEND, MVT::i1)) {
+      N0.getOperand(0).getScalarValueSizeInBits() == 1 &&
+      TLI.getBooleanContents(VT) == TargetLowering::ZeroOrOneBooleanContent) {
     SDValue ZExt = DAG.getNode(ISD::ZERO_EXTEND, DL, VT, N0.getOperand(0));
     return DAG.getNode(ISD::SUB, DL, VT, N1, ZExt);
   }
@@ -2739,6 +2741,17 @@
   if (SDValue V = foldAddSubMasked1(false, N0, N1, DAG, SDLoc(N)))
     return V;
 
+  // If the target's bool is represented as 0/-1, prefer to make this 'add 0/-1'
+  // rather than 'sub 0/1' (the sext should get folded).
+  // sub X, (zext i1 Y) --> add X, (sext i1 Y)
+  if (N1.getOpcode() == ISD::ZERO_EXTEND &&
+      N1.getOperand(0).getScalarValueSizeInBits() == 1 &&
+      TLI.getBooleanContents(VT) ==
+          TargetLowering::ZeroOrNegativeOneBooleanContent) {
+    SDValue SExt = DAG.getNode(ISD::SIGN_EXTEND, DL, VT, N1.getOperand(0));
+    return DAG.getNode(ISD::ADD, DL, VT, N0, SExt);
+  }
+
   // fold Y = sra (X, size(X)-1); sub (xor (X, Y), Y) -> (abs X)
   if (TLI.isOperationLegalOrCustom(ISD::ABS, VT)) {
     if (N0.getOpcode() == ISD::XOR && N1.getOpcode() == ISD::SRA) {


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