[PATCH] D62793: [X86] X86DAGToDAGISel::matchBitExtract(): pattern b: truncation awareness

[Roman Lebedev via Phabricator via llvm-commits]

lebedev.ri updated this revision to Diff 202598.
lebedev.ri added a comment.

Rebased


Repository:
  rL LLVM

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62793/new/

https://reviews.llvm.org/D62793

Files:
  lib/Target/X86/X86ISelDAGToDAG.cpp
  test/CodeGen/X86/extract-bits.ll
  test/CodeGen/X86/extract-lowbits.ll


Index: test/CodeGen/X86/extract-lowbits.ll
===================================================================
--- test/CodeGen/X86/extract-lowbits.ll
+++ test/CodeGen/X86/extract-lowbits.ll
@@ -1770,19 +1770,13 @@
 ;
 ; X64-BMI1NOTBM-LABEL: bzhi64_32_b0:
 ; X64-BMI1NOTBM:       # %bb.0:
-; X64-BMI1NOTBM-NEXT:    movl %esi, %ecx
-; X64-BMI1NOTBM-NEXT:    movq $-1, %rax
-; X64-BMI1NOTBM-NEXT:    # kill: def $cl killed $cl killed $ecx
-; X64-BMI1NOTBM-NEXT:    shlq %cl, %rax
-; X64-BMI1NOTBM-NEXT:    andnl %edi, %eax, %eax
+; X64-BMI1NOTBM-NEXT:    shll $8, %esi
+; X64-BMI1NOTBM-NEXT:    bextrl %esi, %edi, %eax
 ; X64-BMI1NOTBM-NEXT:    retq
 ;
 ; X64-BMI1BMI2-LABEL: bzhi64_32_b0:
 ; X64-BMI1BMI2:       # %bb.0:
-; X64-BMI1BMI2-NEXT:    # kill: def $esi killed $esi def $rsi
-; X64-BMI1BMI2-NEXT:    movq $-1, %rax
-; X64-BMI1BMI2-NEXT:    shlxq %rsi, %rax, %rax
-; X64-BMI1BMI2-NEXT:    andnl %edi, %eax, %eax
+; X64-BMI1BMI2-NEXT:    bzhil %esi, %edi, %eax
 ; X64-BMI1BMI2-NEXT:    retq
   %widenumlowbits = zext i8 %numlowbits to i64
   %notmask = shl nsw i64 -1, %widenumlowbits
Index: test/CodeGen/X86/extract-bits.ll
===================================================================
--- test/CodeGen/X86/extract-bits.ll
+++ test/CodeGen/X86/extract-bits.ll
@@ -3542,22 +3542,17 @@
 ;
 ; X64-BMI1NOTBM-LABEL: bextr64_32_b0:
 ; X64-BMI1NOTBM:       # %bb.0:
-; X64-BMI1NOTBM-NEXT:    movq %rsi, %rcx
-; X64-BMI1NOTBM-NEXT:    # kill: def $cl killed $cl killed $rcx
-; X64-BMI1NOTBM-NEXT:    shrq %cl, %rdi
-; X64-BMI1NOTBM-NEXT:    movq $-1, %rax
-; X64-BMI1NOTBM-NEXT:    movl %edx, %ecx
-; X64-BMI1NOTBM-NEXT:    shlq %cl, %rax
-; X64-BMI1NOTBM-NEXT:    andnl %edi, %eax, %eax
+; X64-BMI1NOTBM-NEXT:    shll $8, %edx
+; X64-BMI1NOTBM-NEXT:    movzbl %sil, %eax
+; X64-BMI1NOTBM-NEXT:    orl %edx, %eax
+; X64-BMI1NOTBM-NEXT:    bextrq %rax, %rdi, %rax
+; X64-BMI1NOTBM-NEXT:    # kill: def $eax killed $eax killed $rax
 ; X64-BMI1NOTBM-NEXT:    retq
 ;
 ; X64-BMI1BMI2-LABEL: bextr64_32_b0:
 ; X64-BMI1BMI2:       # %bb.0:
-; X64-BMI1BMI2-NEXT:    # kill: def $edx killed $edx def $rdx
 ; X64-BMI1BMI2-NEXT:    shrxq %rsi, %rdi, %rax
-; X64-BMI1BMI2-NEXT:    movq $-1, %rcx
-; X64-BMI1BMI2-NEXT:    shlxq %rdx, %rcx, %rcx
-; X64-BMI1BMI2-NEXT:    andnl %eax, %ecx, %eax
+; X64-BMI1BMI2-NEXT:    bzhil %edx, %eax, %eax
 ; X64-BMI1BMI2-NEXT:    retq
   %shiftedval = lshr i64 %val, %numskipbits
   %widenumlowbits = zext i8 %numlowbits to i64
Index: lib/Target/X86/X86ISelDAGToDAG.cpp
===================================================================
--- lib/Target/X86/X86ISelDAGToDAG.cpp
+++ lib/Target/X86/X86ISelDAGToDAG.cpp
@@ -3022,12 +3022,13 @@
   };
 
   // b) x & ~(-1 << nbits)
-  auto matchPatternB = [&checkOneUse, &NBits](SDValue Mask) -> bool {
+  auto matchPatternB = [&checkOneUse, &peekThroughOneUseTruncation,
+                        &NBits](SDValue Mask) -> bool {
     // Match `~()`. Must only have one use!
     if (!isBitwiseNot(Mask) || !checkOneUse(Mask))
       return false;
-    // Match `-1 << nbits`. Must only have one use!
-    SDValue M0 = Mask->getOperand(0);
+    // Match `-1 << nbits`. Might be truncated. Must only have one use!
+    SDValue M0 = peekThroughOneUseTruncation(Mask->getOperand(0));
     if (M0->getOpcode() != ISD::SHL || !checkOneUse(M0))
       return false;
     if (!isAllOnesConstant(M0->getOperand(0)))


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