[PATCH] D60660: [InstCombine] Prune fshl/fshr with masked operands

[Shawn Landden via Phabricator via llvm-commits]

shawnl updated this revision to Diff 195147.

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D60660/new/

https://reviews.llvm.org/D60660

Files:
  lib/Transforms/InstCombine/InstCombineCalls.cpp
  test/Transforms/InstCombine/fsh.ll


Index: test/Transforms/InstCombine/fsh.ll
===================================================================
--- test/Transforms/InstCombine/fsh.ll
+++ test/Transforms/InstCombine/fsh.ll
@@ -560,8 +560,7 @@
 }
 define i32 @fshl_mask_args_same1(i32 %a) {
 ; CHECK-LABEL: @fshl_mask_args_same1(
-; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], -65536
-; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.fshl.i32(i32 [[TMP1]], i32 [[TMP1]], i32 16)
+; CHECK-NEXT:    [[TMP2:%.*]] = lshr i32 [[A:%.*]], 16
 ; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %tmp1 = and i32 %a, 4294901760 ; 0xffff0000
@@ -570,8 +569,8 @@
 }
 define i32 @fshl_mask_args_same2(i32 %a) {
 ; CHECK-LABEL: @fshl_mask_args_same2(
-; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], 255
-; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.fshl.i32(i32 [[TMP1]], i32 [[TMP1]], i32 8)
+; CHECK-NEXT:    [[TMP1:%.*]] = shl i32 [[A:%.*]], 8
+; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[TMP1]], 65280
 ; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %tmp1 = and i32 %a, 255
@@ -580,8 +579,7 @@
 }
 define i32 @fshl_mask_args_same_3(i32 %a) {
 ; CHECK-LABEL: @fshl_mask_args_same_3(
-; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A:%.*]], 255
-; CHECK-NEXT:    [[TMP2:%.*]] = call i32 @llvm.fshl.i32(i32 [[TMP1]], i32 [[TMP1]], i32 24)
+; CHECK-NEXT:    [[TMP2:%.*]] = shl i32 [[A:%.*]], 24
 ; CHECK-NEXT:    ret i32 [[TMP2]]
 ;
   %tmp1 = and i32 %a, 255
@@ -590,9 +588,8 @@
 }
 define i32 @fshl_mask_args_same5(i32 %a) {
 ; CHECK-LABEL: @fshl_mask_args_same5(
-; CHECK-NEXT:    [[TMP2:%.*]] = and i32 [[A:%.*]], -65536
-; CHECK-NEXT:    [[TMP1:%.*]] = and i32 [[A]], -16777216
-; CHECK-NEXT:    [[TMP3:%.*]] = call i32 @llvm.fshl.i32(i32 [[TMP2]], i32 [[TMP1]], i32 17)
+; CHECK-NEXT:    [[TMP1:%.*]] = lshr i32 [[A:%.*]], 15
+; CHECK-NEXT:    [[TMP3:%.*]] = and i32 [[TMP1]], 130560
 ; CHECK-NEXT:    ret i32 [[TMP3]]
 ;
   %tmp2 = and i32 %a, 4294901760 ; 0xfffff00f
@@ -602,8 +599,7 @@
 }
 define <2 x i31> @fshr_mask_args_same_vector(<2 x i31> %a) {
 ; CHECK-LABEL: @fshr_mask_args_same_vector(
-; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i31> [[A:%.*]], <i31 1000, i31 1000>
-; CHECK-NEXT:    [[TMP3:%.*]] = call <2 x i31> @llvm.fshl.v2i31(<2 x i31> [[A]], <2 x i31> [[TMP1]], <2 x i31> <i31 10, i31 10>)
+; CHECK-NEXT:    [[TMP3:%.*]] = shl <2 x i31> [[A:%.*]], <i31 10, i31 10>
 ; CHECK-NEXT:    ret <2 x i31> [[TMP3]]
 ;
   %tmp1 = and <2 x i31> %a, <i31 1000, i31 1000>
@@ -614,7 +610,7 @@
 define <2 x i32> @fshr_mask_args_same_vector2(<2 x i32> %a, <2 x i32> %b) {
 ; CHECK-LABEL: @fshr_mask_args_same_vector2(
 ; CHECK-NEXT:    [[TMP1:%.*]] = and <2 x i32> [[A:%.*]], <i32 1000000, i32 100000>
-; CHECK-NEXT:    [[TMP3:%.*]] = call <2 x i32> @llvm.fshl.v2i32(<2 x i32> [[TMP1]], <2 x i32> [[TMP1]], <2 x i32> <i32 29, i32 29>)
+; CHECK-NEXT:    [[TMP3:%.*]] = lshr exact <2 x i32> [[TMP1]], <i32 3, i32 3>
 ; CHECK-NEXT:    ret <2 x i32> [[TMP3]]
 ;
   %tmp1 = and <2 x i32> %a, <i32 1000000, i32 100000>
Index: lib/Transforms/InstCombine/InstCombineCalls.cpp
===================================================================
--- lib/Transforms/InstCombine/InstCombineCalls.cpp
+++ lib/Transforms/InstCombine/InstCombineCalls.cpp
@@ -2085,6 +2085,9 @@
                                           ConstantExpr::getSub(WidthC, ShAmtC));
     }
 
+    // Left or right might be masked
+    if (SimplifyDemandedInstructionBits(*II))
+      return &CI;
     // The shift amount (operand 2) of a funnel shift is modulo the bitwidth,
     // so only the low bits of the shift amount are demanded if the bitwidth is
     // a power-of-2.


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