[PATCH] D23677: [AArch64] Avoid materializing -1 values when generating csinv instructions.

[Chad Rosier via llvm-commits]

mcrosier retitled this revision from "[AArch64] Reuse register with known value when generating csneg and csinv instructions." to "[AArch64] Avoid materializing -1 values when generating csinv instructions.".
mcrosier updated the summary for this revision.
mcrosier updated this revision to Diff 68597.

https://reviews.llvm.org/D23677

Files:
  lib/Target/AArch64/AArch64ISelLowering.cpp
  test/CodeGen/AArch64/arm64-csel.ll

Index: test/CodeGen/AArch64/arm64-csel.ll
===================================================================
--- test/CodeGen/AArch64/arm64-csel.ll
+++ test/CodeGen/AArch64/arm64-csel.ll
@@ -228,3 +228,37 @@
   %inc.c = add i64 %inc, %c
   ret i64 %inc.c
 }
+
+; PR28965
+define i32 @foo20(i32 %x) {
+entry:
+; CHECK-LABEL: foo20:
+; CHECK: cmp w[[REG:[0-9]+]], #1
+; CHECK-NOT: orr w{{[0-9]+}}, wzr, #0x1
+; CHECK: csinv w0, w[[REG]], wzr, eq
+  %cmp = icmp eq i32 %x, 1
+  %res = select i1 %cmp, i32 1, i32 -1
+  ret i32 %res
+}
+
+define i64 @foo21(i64 %x) {
+entry:
+; CHECK-LABEL: foo21:
+; CHECK: cmp x[[REG:[0-9]+]], #1
+; CHECK-NOT: orr w{{[0-9]+}}, wzr, #0x1
+; CHECK: csinv x0, x[[REG]], xzr, eq
+  %cmp = icmp eq i64 %x, 1
+  %res = select i1 %cmp, i64 1, i64 -1
+  ret i64 %res
+}
+
+define i64 @foo22(i64 %x) {
+entry:
+; CHECK-LABEL: foo22:
+; CHECK: cmp x[[REG:[0-9]+]], #3
+; CHECK-NOT: orr w{{[0-9]+}}, wzr, #0x3
+; CHECK: csinv x0, x[[REG]], xzr, eq
+  %cmp = icmp eq i64 %x, 3
+  %res = select i1 %cmp, i64 3, i64 -1
+  ret i64 %res
+}
Index: lib/Target/AArch64/AArch64ISelLowering.cpp
===================================================================
--- lib/Target/AArch64/AArch64ISelLowering.cpp
+++ lib/Target/AArch64/AArch64ISelLowering.cpp
@@ -3988,13 +3988,25 @@
     } else if (CTVal && CFVal) {
       const int64_t TrueVal = CTVal->getSExtValue();
       const int64_t FalseVal = CFVal->getSExtValue();
+      ConstantSDNode *RHSVal = dyn_cast<ConstantSDNode>(RHS);
       bool Swap = false;
+      bool KeepFVal = false;
 
       // If both TVal and FVal are constants, see if FVal is the
       // inverse/negation/increment of TVal and generate a CSINV/CSNEG/CSINC
       // instead of a CSEL in that case.
       if (TrueVal == ~FalseVal) {
         Opcode = AArch64ISD::CSINV;
+      } else if (CFVal->isAllOnesValue() && RHSVal == CTVal &&
+                 changeIntCCToAArch64CC(CC) == AArch64CC::EQ) {
+        // If FVal is -1, we can use a CSINV to invert wzr/xzr to avoid
+        // materializing the -1.  We can also avoid materializing TVal, if TVal
+        // matches RHS and we're doing an equality comparison as we know LHS
+        // will contain TVal if the equality is true.
+        Opcode = AArch64ISD::CSINV;
+        TVal = LHS;
+        FVal = DAG.getConstant(0, dl, FVal.getValueType());
+        KeepFVal = true;
       } else if (TrueVal == -FalseVal) {
         Opcode = AArch64ISD::CSNEG;
       } else if (TVal.getValueType() == MVT::i32) {
@@ -4029,7 +4041,7 @@
         CC = ISD::getSetCCInverse(CC, true);
       }
 
-      if (Opcode != AArch64ISD::CSEL) {
+      if (Opcode != AArch64ISD::CSEL && !KeepFVal) {
         // Drop FVal since we can get its value by simply inverting/negating
         // TVal.
         FVal = TVal;


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