[PATCH] D43346: [X86] Enable BT to be used in place of TEST for single bit checks under optsize

[Craig Topper via Phabricator via llvm-commits]

craig.topper updated this revision to Diff 134481.
craig.topper added a comment.

Don't do this immediates that fit in a byte, It won't save anything


https://reviews.llvm.org/D43346

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/test-vs-bittest.ll


Index: test/CodeGen/X86/test-vs-bittest.ll
===================================================================
--- test/CodeGen/X86/test-vs-bittest.ll
+++ test/CodeGen/X86/test-vs-bittest.ll
@@ -75,8 +75,8 @@
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    pushq %rax
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    testl $2048, %edi # imm = 0x800
-; CHECK-NEXT:    je .LBB3_2
+; CHECK-NEXT:    btl $11, %edi
+; CHECK-NEXT:    jae .LBB3_2
 ; CHECK-NEXT:  # %bb.1: # %yes
 ; CHECK-NEXT:    callq bar
 ; CHECK-NEXT:  .LBB3_2: # %no
@@ -259,8 +259,8 @@
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    pushq %rax
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    testl $2048, %edi # imm = 0x800
-; CHECK-NEXT:    je .LBB11_2
+; CHECK-NEXT:    btl $11, %edi
+; CHECK-NEXT:    jae .LBB11_2
 ; CHECK-NEXT:  # %bb.1: # %yes
 ; CHECK-NEXT:    callq bar
 ; CHECK-NEXT:  .LBB11_2: # %no
@@ -351,8 +351,8 @@
 ; CHECK:       # %bb.0:
 ; CHECK-NEXT:    pushq %rax
 ; CHECK-NEXT:    .cfi_def_cfa_offset 16
-; CHECK-NEXT:    testl $2048, %edi # imm = 0x800
-; CHECK-NEXT:    je .LBB15_2
+; CHECK-NEXT:    btl $11, %edi
+; CHECK-NEXT:    jae .LBB15_2
 ; CHECK-NEXT:  # %bb.1: # %yes
 ; CHECK-NEXT:    callq bar
 ; CHECK-NEXT:  .LBB15_2: # %no
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -17709,12 +17709,15 @@
     if (AndRHSVal == 1 && AndLHS.getOpcode() == ISD::SRL) {
       LHS = AndLHS.getOperand(0);
       RHS = AndLHS.getOperand(1);
-    }
-
-    // Use BT if the immediate can't be encoded in a TEST instruction.
-    if (!isUInt<32>(AndRHSVal) && isPowerOf2_64(AndRHSVal)) {
-      LHS = AndLHS;
-      RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), dl, LHS.getValueType());
+    } else {
+      // Use BT if the immediate can't be encoded in a TEST instruction or we
+      // are optimizing for size and the immedaite won't fit in a byte.
+      bool OptForSize = DAG.getMachineFunction().getFunction().optForSize();
+      if ((!isUInt<32>(AndRHSVal) || (OptForSize && !isUInt<8>(AndRHSVal))) &&
+          isPowerOf2_64(AndRHSVal)) {
+        LHS = AndLHS;
+        RHS = DAG.getConstant(Log2_64_Ceil(AndRHSVal), dl, LHS.getValueType());
+      }
     }
   }
 


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