[PATCH] D58870: [X86] Enable 8-bit SHL to convert to LEA

[Craig Topper via Phabricator via llvm-commits]

craig.topper created this revision.
craig.topper added reviewers: spatel, RKSimon.

https://reviews.llvm.org/D58870

Files:
  lib/Target/X86/X86InstrInfo.cpp
  lib/Target/X86/X86InstrShiftRotate.td
  test/CodeGen/X86/fast-isel-shift.ll
  test/CodeGen/X86/mul-constant-i8.ll


Index: test/CodeGen/X86/mul-constant-i8.ll
===================================================================
--- test/CodeGen/X86/mul-constant-i8.ll
+++ test/CodeGen/X86/mul-constant-i8.ll
@@ -36,8 +36,8 @@
 define i8 @test_mul_by_4(i8 %x) {
 ; X64-LABEL: test_mul_by_4:
 ; X64:       # %bb.0:
-; X64-NEXT:    movl %edi, %eax
-; X64-NEXT:    shlb $2, %al
+; X64-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-NEXT:    leal (,%rdi,4), %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
   %m = mul i8 %x, 4
@@ -82,8 +82,8 @@
 define i8 @test_mul_by_8(i8 %x) {
 ; X64-LABEL: test_mul_by_8:
 ; X64:       # %bb.0:
-; X64-NEXT:    movl %edi, %eax
-; X64-NEXT:    shlb $3, %al
+; X64-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-NEXT:    leal (,%rdi,8), %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
   %m = mul i8 %x, 8
@@ -449,8 +449,8 @@
 define i8 @test_mul_by_520(i8 %x) {
 ; X64-LABEL: test_mul_by_520:
 ; X64:       # %bb.0:
-; X64-NEXT:    movl %edi, %eax
-; X64-NEXT:    shlb $3, %al
+; X64-NEXT:    # kill: def $edi killed $edi def $rdi
+; X64-NEXT:    leal (,%rdi,8), %eax
 ; X64-NEXT:    # kill: def $al killed $al killed $eax
 ; X64-NEXT:    retq
   %m = mul i8 %x, 520
Index: test/CodeGen/X86/fast-isel-shift.ll
===================================================================
--- test/CodeGen/X86/fast-isel-shift.ll
+++ test/CodeGen/X86/fast-isel-shift.ll
@@ -157,8 +157,8 @@
 define i8 @shl_imm1_i8(i8 %a) {
 ; CHECK-LABEL: shl_imm1_i8:
 ; CHECK:       ## %bb.0:
-; CHECK-NEXT:    movl %edi, %eax
-; CHECK-NEXT:    shlb $1, %al
+; CHECK-NEXT:    ## kill: def $edi killed $edi def $rdi
+; CHECK-NEXT:    leal (,%rdi,2), %eax
 ; CHECK-NEXT:    ## kill: def $al killed $al killed $eax
 ; CHECK-NEXT:    retq
   %c = shl i8 %a, 1
Index: lib/Target/X86/X86InstrShiftRotate.td
===================================================================
--- lib/Target/X86/X86InstrShiftRotate.td
+++ lib/Target/X86/X86InstrShiftRotate.td
@@ -30,11 +30,11 @@
                   [(set GR64:$dst, (shl GR64:$src1, CL))]>;
 } // Uses = [CL], SchedRW
 
+let isConvertibleToThreeAddress = 1 in {   // Can transform into LEA.
 def SHL8ri   : Ii8<0xC0, MRM4r, (outs GR8 :$dst), (ins GR8 :$src1, u8imm:$src2),
                    "shl{b}\t{$src2, $dst|$dst, $src2}",
                    [(set GR8:$dst, (shl GR8:$src1, (i8 imm:$src2)))]>;
 
-let isConvertibleToThreeAddress = 1 in {   // Can transform into LEA.
 def SHL16ri  : Ii8<0xC1, MRM4r, (outs GR16:$dst), (ins GR16:$src1, u8imm:$src2),
                    "shl{w}\t{$src2, $dst|$dst, $src2}",
                    [(set GR16:$dst, (shl GR16:$src1, (i8 imm:$src2)))]>,
Index: lib/Target/X86/X86InstrInfo.cpp
===================================================================
--- lib/Target/X86/X86InstrInfo.cpp
+++ lib/Target/X86/X86InstrInfo.cpp
@@ -755,6 +755,7 @@
       BuildMI(*MFI, MBBI, MI.getDebugLoc(), get(Opcode), OutRegLEA);
   switch (MIOpc) {
   default: llvm_unreachable("Unreachable!");
+  case X86::SHL8ri:
   case X86::SHL16ri: {
     unsigned ShAmt = MI.getOperand(2).getImm();
     MIB.addReg(0).addImm(1ULL << ShAmt)
@@ -918,6 +919,9 @@
 
     break;
   }
+  case X86::SHL8ri:
+    Is8BitOp = true;
+    LLVM_FALLTHROUGH;
   case X86::SHL16ri: {
     assert(MI.getNumOperands() >= 3 && "Unknown shift instruction!");
     unsigned ShAmt = getTruncatedShiftCount(MI, 2);


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