[llvm] r325290 - [X86] Enable BT to be used in place of TEST for single bit checks under optsize

[Craig Topper via llvm-commits]

Author: ctopper
Date: Thu Feb 15 12:27:30 2018
New Revision: 325290

URL: http://llvm.org/viewvc/llvm-project?rev=325290&view=rev
Log:
[X86] Enable BT to be used in place of TEST for single bit checks under optsize

We already do this for 64-bit when it won't fit into a 64-bit AND/TEST's immediate field. This adds an additional qualifier to do it for any single bit constant larger than 8-bits under optsize

Differential Revision: https://reviews.llvm.org/D43346

Modified:
    llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
    llvm/trunk/test/CodeGen/X86/test-vs-bittest.ll

Modified: llvm/trunk/lib/Target/X86/X86ISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86ISelLowering.cpp?rev=325290&r1=325289&r2=325290&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86ISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86ISelLowering.cpp Thu Feb 15 12:27:30 2018
@@ -17709,12 +17709,15 @@ static SDValue LowerAndToBT(SDValue And,
     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());
+      }
     }
   }
 

Modified: llvm/trunk/test/CodeGen/X86/test-vs-bittest.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/X86/test-vs-bittest.ll?rev=325290&r1=325289&r2=325290&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/X86/test-vs-bittest.ll (original)
+++ llvm/trunk/test/CodeGen/X86/test-vs-bittest.ll Thu Feb 15 12:27:30 2018
@@ -75,8 +75,8 @@ define void @test64_optsize_2(i64 inreg
 ; 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 @@ define void @test32_optsize_2(i32 inreg
 ; 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 @@ define void @test16_optsize_2(i16 inreg
 ; 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