[llvm] r313829 - [SimplifyCFG] don't create a no-op subtract
Sanjay Patel via llvm-commits
llvm-commits at lists.llvm.org
Wed Sep 20 15:31:35 PDT 2017
Author: spatel
Date: Wed Sep 20 15:31:35 2017
New Revision: 313829
URL: http://llvm.org/viewvc/llvm-project?rev=313829&view=rev
Log:
[SimplifyCFG] don't create a no-op subtract
I noticed this inefficiency while investigating PR34603:
https://bugs.llvm.org/show_bug.cgi?id=34603
This fix will likely push another bug (we don't maintain state of 'LateSimplifyCFG')
into hiding, but I'll try to clean that up with a follow-up patch anyway.
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
llvm/trunk/test/Transforms/SimplifyCFG/rangereduce.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=313829&r1=313828&r2=313829&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Wed Sep 20 15:31:35 2017
@@ -5275,8 +5275,12 @@ static bool SwitchToLookupTable(SwitchIn
// Compute the table index value.
Builder.SetInsertPoint(SI);
- Value *TableIndex =
- Builder.CreateSub(SI->getCondition(), MinCaseVal, "switch.tableidx");
+ Value *TableIndex;
+ if (MinCaseVal->isNullValue())
+ TableIndex = SI->getCondition();
+ else
+ TableIndex = Builder.CreateSub(SI->getCondition(), MinCaseVal,
+ "switch.tableidx");
// Compute the maximum table size representable by the integer type we are
// switching upon.
Modified: llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll?rev=313829&r1=313828&r2=313829&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll Wed Sep 20 15:31:35 2017
@@ -90,14 +90,13 @@ sw.epilog:
; CHECK-LABEL: @h(
; CHECK: entry:
-; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
-; CHECK-NEXT: %0 = icmp ult i32 %switch.tableidx, 4
+; CHECK-NEXT: %0 = icmp ult i32 %x, 4
; CHECK-NEXT: br i1 %0, label %switch.lookup, label %sw.epilog
; CHECK: switch.lookup:
-; CHECK-NEXT: %switch.shiftamt = mul i32 %switch.tableidx, 8
+; CHECK-NEXT: %switch.shiftamt = mul i32 %x, 8
; CHECK-NEXT: %switch.downshift = lshr i32 89655594, %switch.shiftamt
; CHECK-NEXT: %switch.masked = trunc i32 %switch.downshift to i8
-; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x float], [4 x float]* @switch.table.h, i32 0, i32 %switch.tableidx
+; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x float], [4 x float]* @switch.table.h, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load float, float* %switch.gep
; CHECK-NEXT: br label %sw.epilog
; CHECK: sw.epilog:
@@ -140,11 +139,10 @@ return:
; CHECK-LABEL: @foostring(
; CHECK: entry:
-; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
-; CHECK-NEXT: %0 = icmp ult i32 %switch.tableidx, 4
+; CHECK-NEXT: %0 = icmp ult i32 %x, 4
; CHECK-NEXT: br i1 %0, label %switch.lookup, label %return
; CHECK: switch.lookup:
-; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i8*], [4 x i8*]* @switch.table.foostring, i32 0, i32 %switch.tableidx
+; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i8*], [4 x i8*]* @switch.table.foostring, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i8*, i8** %switch.gep
; CHECK-NEXT: ret i8* %switch.load
}
@@ -173,7 +171,7 @@ sw.epilog:
; CHECK-LABEL: @earlyreturncrash(
; CHECK: switch.lookup:
-; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.earlyreturncrash, i32 0, i32 %switch.tableidx
+; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.earlyreturncrash, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i32, i32* %switch.gep
; CHECK-NEXT: ret i32 %switch.load
; CHECK: sw.epilog:
@@ -285,7 +283,7 @@ bb3:
%tmp4 = phi i1 [ undef, %bb ], [ false, %bb2 ], [ true, %bb1 ]
ret i1 %tmp4
; CHECK-LABEL: define i1 @undef(
-; CHECK: %switch.cast = trunc i32 %switch.tableidx to i9
+; CHECK: %switch.cast = trunc i32 %tmp to i9
; CHECK: %switch.downshift = lshr i9 3, %switch.shiftamt
}
@@ -778,7 +776,7 @@ return:
; CHECK-LABEL: @unreachable_case(
; CHECK: switch.lookup:
-; CHECK: getelementptr inbounds [9 x i32], [9 x i32]* @switch.table.unreachable_case, i32 0, i32 %switch.tableidx
+; CHECK: getelementptr inbounds [9 x i32], [9 x i32]* @switch.table.unreachable_case, i32 0, i32 %x
}
define i32 @unreachable_default(i32 %x) {
@@ -802,10 +800,9 @@ return:
; CHECK-LABEL: @unreachable_default(
; CHECK: entry:
-; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
; CHECK-NOT: icmp
; CHECK-NOT: br 1i
-; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.unreachable_default, i32 0, i32 %switch.tableidx
+; CHECK-NEXT: %switch.gep = getelementptr inbounds [4 x i32], [4 x i32]* @switch.table.unreachable_default, i32 0, i32 %x
; CHECK-NEXT: %switch.load = load i32, i32* %switch.gep
; CHECK-NEXT: ret i32 %switch.load
}
@@ -884,7 +881,7 @@ return:
; CHECK: entry:
; CHECK: br i1 %{{.*}}, label %switch.hole_check, label %sw.default
; CHECK: switch.hole_check:
-; CHECK-NEXT: %switch.maskindex = trunc i32 %switch.tableidx to i8
+; CHECK-NEXT: %switch.maskindex = trunc i32 %c to i8
; CHECK-NEXT: %switch.shifted = lshr i8 47, %switch.maskindex
; The mask is binary 101111.
; CHECK-NEXT: %switch.lobit = trunc i8 %switch.shifted to i1
@@ -915,11 +912,10 @@ return:
define i32 @threecases(i32 %c) {
; CHECK-LABEL: @threecases(
; CHECK-NEXT: entry:
-; CHECK-NEXT: [[SWITCH_TABLEIDX:%.*]] = sub i32 %c, 0
-; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 [[SWITCH_TABLEIDX]], 3
+; CHECK-NEXT: [[TMP0:%.*]] = icmp ult i32 %c, 3
; CHECK-NEXT: br i1 [[TMP0]], label %switch.lookup, label %return
; CHECK: switch.lookup:
-; CHECK-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x i32], [3 x i32]* @switch.table.threecases, i32 0, i32 [[SWITCH_TABLEIDX]]
+; CHECK-NEXT: [[SWITCH_GEP:%.*]] = getelementptr inbounds [3 x i32], [3 x i32]* @switch.table.threecases, i32 0, i32 %c
; CHECK-NEXT: [[SWITCH_LOAD:%.*]] = load i32, i32* [[SWITCH_GEP]]
; CHECK-NEXT: ret i32 [[SWITCH_LOAD]]
; CHECK: return:
@@ -1146,8 +1142,7 @@ return:
ret i32 %retval.0
; CHECK-LABEL: @reuse_cmp1(
; CHECK: entry:
-; CHECK-NEXT: %switch.tableidx = sub i32 %x, 0
-; CHECK-NEXT: [[C:%.+]] = icmp ult i32 %switch.tableidx, 4
+; CHECK-NEXT: [[C:%.+]] = icmp ult i32 %x, 4
; CHECK-NEXT: %inverted.cmp = xor i1 [[C]], true
; CHECK: [[R:%.+]] = select i1 %inverted.cmp, i32 100, i32 {{.*}}
; CHECK-NEXT: ret i32 [[R]]
Modified: llvm/trunk/test/Transforms/SimplifyCFG/rangereduce.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/rangereduce.ll?rev=313829&r1=313828&r2=313829&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/rangereduce.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/rangereduce.ll Wed Sep 20 15:31:35 2017
@@ -235,11 +235,10 @@ define i8 @test7(i8 %a) optsize {
; CHECK-NEXT: [[TMP2:%.*]] = lshr i8 [[TMP1]], 2
; CHECK-NEXT: [[TMP3:%.*]] = shl i8 [[TMP1]], 6
; CHECK-NEXT: [[TMP4:%.*]] = or i8 [[TMP2]], [[TMP3]]
-; CHECK-NEXT: [[SWITCH_TABLEIDX:%.*]] = sub i8 [[TMP4]], 0
-; CHECK-NEXT: [[TMP5:%.*]] = icmp ult i8 [[SWITCH_TABLEIDX]], 4
+; CHECK-NEXT: [[TMP5:%.*]] = icmp ult i8 [[TMP4]], 4
; CHECK-NEXT: br i1 [[TMP5]], label [[SWITCH_LOOKUP:%.*]], label [[DEF:%.*]]
; CHECK: switch.lookup:
-; CHECK-NEXT: [[SWITCH_CAST:%.*]] = zext i8 [[SWITCH_TABLEIDX]] to i32
+; CHECK-NEXT: [[SWITCH_CAST:%.*]] = zext i8 [[TMP4]] to i32
; CHECK-NEXT: [[SWITCH_SHIFTAMT:%.*]] = mul i32 [[SWITCH_CAST]], 8
; CHECK-NEXT: [[SWITCH_DOWNSHIFT:%.*]] = lshr i32 -943228976, [[SWITCH_SHIFTAMT]]
; CHECK-NEXT: [[SWITCH_MASKED:%.*]] = trunc i32 [[SWITCH_DOWNSHIFT]] to i8
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