commit 14d06327d7ec895606138ab3666c56174c459c00
author Simon Pilgrim <llvm-dev@redking.me.uk> Fri Apr 01 17:22:33 2022 +0100
committer Copybara-Service <copybara-worker@google.com> Fri Apr 01 09:29:20 2022 -0700
tree b9fb7f1123c26b2fc36bdd7d959028d7712c3c07
parent 2ae64701900d856e4fe10547a4ee6a80e32931dd

[X86] matchAddressRecursively - add XOR(X, MIN_SIGNED_VALUE) handling

Allows us to fold XOR(X, MIN_SIGNED_VALUE) == ADD(X, MIN_SIGNED_VALUE) into LEA patterns

As mentioned on PR52267.

Differential Revision: https://reviews.llvm.org/D122815

GitOrigin-RevId: c64f37f818b7a928b48540920d6e0c6df8903128

lib/Target/X86/X86ISelDAGToDAG.cpp

diff --git a/lib/Target/X86/X86ISelDAGToDAG.cpp b/lib/Target/X86/X86ISelDAGToDAG.cpp
index aab534d..f7c365c 100644
--- a/lib/Target/X86/X86ISelDAGToDAG.cpp
+++ b/lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -2431,6 +2431,15 @@
       return false;
     break;
 
+  case ISD::XOR:
+    // We want to look through a transform in InstCombine that
+    // turns 'add' with min_signed_val into 'xor', so we can treat this 'xor'
+    // exactly like an 'add'.
+    if (auto *NC1 = dyn_cast<ConstantSDNode>(N.getOperand(1)))
+      if (NC1->isMinSignedValue() && !matchAdd(N, AM, Depth))
+        return false;
+    break;
+
   case ISD::AND: {
     // Perform some heroic transforms on an and of a constant-count shift
     // with a constant to enable use of the scaled offset field.

lib/Target/X86/X86InstrInfo.td

diff --git a/lib/Target/X86/X86InstrInfo.td b/lib/Target/X86/X86InstrInfo.td
index f464b72..50626cf 100644
--- a/lib/Target/X86/X86InstrInfo.td
+++ b/lib/Target/X86/X86InstrInfo.td
@@ -840,11 +840,11 @@
 // Define X86-specific addressing mode.
 def addr      : ComplexPattern<iPTR, 5, "selectAddr", [], [SDNPWantParent]>;
 def lea32addr : ComplexPattern<i32, 5, "selectLEAAddr",
-                               [add, sub, mul, X86mul_imm, shl, or, frameindex],
+                               [add, sub, mul, X86mul_imm, shl, or, xor, frameindex],
                                []>;
 // In 64-bit mode 32-bit LEAs can use RIP-relative addressing.
 def lea64_32addr : ComplexPattern<i32, 5, "selectLEA64_32Addr",
-                                  [add, sub, mul, X86mul_imm, shl, or,
+                                  [add, sub, mul, X86mul_imm, shl, or, xor,
                                    frameindex, X86WrapperRIP],
                                   []>;
 
@@ -855,7 +855,7 @@
                                [tglobaltlsaddr], []>;
 
 def lea64addr : ComplexPattern<i64, 5, "selectLEAAddr",
-                        [add, sub, mul, X86mul_imm, shl, or, frameindex,
+                        [add, sub, mul, X86mul_imm, shl, or, xor, frameindex,
                          X86WrapperRIP], []>;
 
 def tls64addr : ComplexPattern<i64, 5, "selectTLSADDRAddr",

test/CodeGen/X86/xor-lea.ll

diff --git a/test/CodeGen/X86/xor-lea.ll b/test/CodeGen/X86/xor-lea.ll
index 9876854..a4d5920 100644
--- a/test/CodeGen/X86/xor-lea.ll
+++ b/test/CodeGen/X86/xor-lea.ll
@@ -257,8 +257,8 @@
 ; X64-LABEL: sub_xor_sminval_i32:
 ; X64:       # %bb.0:
 ; X64-NEXT:    # kill: def $edi killed $edi def $rdi
-; X64-NEXT:    xorl $-2147483648, %edi # imm = 0x80000000
-; X64-NEXT:    leal -512(%rdi), %eax
+; X64-NEXT:    movl $-512, %eax # imm = 0xFE00
+; X64-NEXT:    leal -2147483648(%rdi,%rax), %eax
 ; X64-NEXT:    retq
   %r = xor i32 %x, 2147483648
   %s = sub i32 %r, 512
@@ -335,15 +335,13 @@
 ; X86-LABEL: xor_shl_sminval_i32:
 ; X86:       # %bb.0:
 ; X86-NEXT:    movl {{[0-9]+}}(%esp), %eax
-; X86-NEXT:    shll $3, %eax
-; X86-NEXT:    xorl $-2147483648, %eax # imm = 0x80000000
+; X86-NEXT:    leal -2147483648(,%eax,8), %eax
 ; X86-NEXT:    retl
 ;
 ; X64-LABEL: xor_shl_sminval_i32:
 ; X64:       # %bb.0:
 ; X64-NEXT:    # kill: def $edi killed $edi def $rdi
-; X64-NEXT:    leal (,%rdi,8), %eax
-; X64-NEXT:    xorl $-2147483648, %eax # imm = 0x80000000
+; X64-NEXT:    leal -2147483648(,%rdi,8), %eax
 ; X64-NEXT:    retq
   %s = shl i32 %x, 3
   %r = xor i32 %s, 2147483648
@@ -382,9 +380,8 @@
 ;
 ; X64-LABEL: xor_shl_sminval_i64:
 ; X64:       # %bb.0:
-; X64-NEXT:    leaq (,%rdi,4), %rcx
 ; X64-NEXT:    movabsq $-9223372036854775808, %rax # imm = 0x8000000000000000
-; X64-NEXT:    xorq %rcx, %rax
+; X64-NEXT:    leaq (%rax,%rdi,4), %rax
 ; X64-NEXT:    retq
   %s = shl i64 %x, 2
   %r = xor i64 %s, -9223372036854775808