[AMDGPU] Recognize x & ~(-1 << y) pattern.

[lebedev.ri]

Summary

The same pattern as D48010, but this one is IR-canonical as of D47428.

[arsenm]

LGTM

[lebedev.ri]

In D48012#1128257, @arsenm wrote:

LGTM

Thank you for the review!

llvm/trunk/lib/Target/AMDGPU/AMDGPUInstructions.td

multiclass BFEPattern <Instruction UBFE, Instruction SBFE, Instruction MOV> {
   >;
 
   // x & ((1 << y) - 1)
   def : AMDGPUPat <
     (and i32:$src, (add_oneuse (shl_oneuse 1, i32:$width), -1)),
     (UBFE $src, (i32 0), $width)
   >;
 
+  // x & ~(-1 << y)
+  def : AMDGPUPat <
+    (and i32:$src, (xor_oneuse (shl_oneuse -1, i32:$width), -1)),
+    (UBFE $src, (i32 0), $width)
+  >;
+
   // x & (-1 >> (bitwidth - y))
   def : AMDGPUPat <
     (and i32:$src, (srl_oneuse -1, (sub 32, i32:$width))),
     (UBFE $src, (i32 0), $width)
   >;
 
   // x << (bitwidth - y) >> (bitwidth - y)
   def : AMDGPUPat <

llvm/trunk/test/CodeGen/AMDGPU/extract-lowbits.ll

; GCN-NEXT:    s_setpc_b64 s[30:31]
   ret i32 %masked
 }
 
 ; ---------------------------------------------------------------------------- ;
 ; Pattern b. 32-bit
 ; ---------------------------------------------------------------------------- ;
 
 define i32 @bzhi32_b0(i32 %val, i32 %numlowbits) nounwind {
-; SI-LABEL: bzhi32_b0:
-; SI:       ; %bb.0:
-; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; SI-NEXT:    v_lshl_b32_e32 v1, -1, v1
-; SI-NEXT:    v_not_b32_e32 v1, v1
-; SI-NEXT:    v_and_b32_e32 v0, v1, v0
-; SI-NEXT:    s_setpc_b64 s[30:31]
-;
-; VI-LABEL: bzhi32_b0:
-; VI:       ; %bb.0:
-; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e64 v1, v1, -1
-; VI-NEXT:    v_not_b32_e32 v1, v1
-; VI-NEXT:    v_and_b32_e32 v0, v1, v0
-; VI-NEXT:    s_setpc_b64 s[30:31]
+; GCN-LABEL: bzhi32_b0:
+; GCN:       ; %bb.0:
+; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GCN-NEXT:    v_bfe_u32 v0, v0, 0, v1
+; GCN-NEXT:    s_setpc_b64 s[30:31]
   %notmask = shl i32 -1, %numlowbits
   %mask = xor i32 %notmask, -1
   %masked = and i32 %mask, %val
   ret i32 %masked
 }
 
 define i32 @bzhi32_b1_indexzext(i32 %val, i8 zeroext %numlowbits) nounwind {
-; SI-LABEL: bzhi32_b1_indexzext:
-; SI:       ; %bb.0:
-; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; SI-NEXT:    v_lshl_b32_e32 v1, -1, v1
-; SI-NEXT:    v_not_b32_e32 v1, v1
-; SI-NEXT:    v_and_b32_e32 v0, v1, v0
-; SI-NEXT:    s_setpc_b64 s[30:31]
-;
-; VI-LABEL: bzhi32_b1_indexzext:
-; VI:       ; %bb.0:
-; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e64 v1, v1, -1
-; VI-NEXT:    v_not_b32_e32 v1, v1
-; VI-NEXT:    v_and_b32_e32 v0, v1, v0
-; VI-NEXT:    s_setpc_b64 s[30:31]
+; GCN-LABEL: bzhi32_b1_indexzext:
+; GCN:       ; %bb.0:
+; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GCN-NEXT:    v_bfe_u32 v0, v0, 0, v1
+; GCN-NEXT:    s_setpc_b64 s[30:31]
   %conv = zext i8 %numlowbits to i32
   %notmask = shl i32 -1, %conv
   %mask = xor i32 %notmask, -1
   %masked = and i32 %mask, %val
   ret i32 %masked
 }
 
 define i32 @bzhi32_b4_commutative(i32 %val, i32 %numlowbits) nounwind {
-; SI-LABEL: bzhi32_b4_commutative:
-; SI:       ; %bb.0:
-; SI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; SI-NEXT:    v_lshl_b32_e32 v1, -1, v1
-; SI-NEXT:    v_not_b32_e32 v1, v1
-; SI-NEXT:    v_and_b32_e32 v0, v0, v1
-; SI-NEXT:    s_setpc_b64 s[30:31]
-;
-; VI-LABEL: bzhi32_b4_commutative:
-; VI:       ; %bb.0:
-; VI-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
-; VI-NEXT:    v_lshlrev_b32_e64 v1, v1, -1
-; VI-NEXT:    v_not_b32_e32 v1, v1
-; VI-NEXT:    v_and_b32_e32 v0, v0, v1
-; VI-NEXT:    s_setpc_b64 s[30:31]
+; GCN-LABEL: bzhi32_b4_commutative:
+; GCN:       ; %bb.0:
+; GCN-NEXT:    s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)
+; GCN-NEXT:    v_bfe_u32 v0, v0, 0, v1
+; GCN-NEXT:    s_setpc_b64 s[30:31]
   %notmask = shl i32 -1, %numlowbits
   %mask = xor i32 %notmask, -1
   %masked = and i32 %val, %mask ; swapped order
   ret i32 %masked
 }
 
 ; ---------------------------------------------------------------------------- ;
 ; Pattern c. 32-bit