[llvm] r255489 - Don't create unnecessary PHIs
James Molloy via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 14 02:57:02 PST 2015
Author: jamesm
Date: Mon Dec 14 04:57:01 2015
New Revision: 255489
URL: http://llvm.org/viewvc/llvm-project?rev=255489&view=rev
Log:
Don't create unnecessary PHIs
In conditional store merging, we were creating PHIs when we didn't
need to. If the value to be predicated isn't defined in the block
we're predicating, then it doesn't need a PHI at all (because we only
deal with triangles and diamonds, any value not in the predicated BB
must dominate the predicated BB).
This fixes a large code size increase in some benchmarks in a popular embedded benchmark suite.
Added:
llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
Modified:
llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores.ll
Modified: llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp?rev=255489&r1=255488&r2=255489&view=diff
==============================================================================
--- llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp (original)
+++ llvm/trunk/lib/Transforms/Utils/SimplifyCFG.cpp Mon Dec 14 04:57:01 2015
@@ -2385,6 +2385,11 @@ static Value *ensureValueAvailableInSucc
// If AlternativeV is not nullptr, we care about both incoming values in PHI.
// PHI must be exactly: phi <ty> [ %BB, %V ], [ %OtherBB, %AlternativeV]
// where OtherBB is the single other predecessor of BB's only successor.
+
+ // If V is not an instruction defined in BB, just return it.
+ if (!isa<Instruction>(V) || cast<Instruction>(V)->getParent() != BB)
+ return V;
+
PHINode *PHI = nullptr;
BasicBlock *Succ = BB->getSingleSuccessor();
Added: llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll?rev=255489&view=auto
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll (added)
+++ llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores-2.ll Mon Dec 14 04:57:01 2015
@@ -0,0 +1,198 @@
+; RUN: opt -S < %s -simplifycfg -simplifycfg-merge-cond-stores=true -simplifycfg-merge-cond-stores-aggressively=false -phi-node-folding-threshold=2 | FileCheck %s
+
+target datalayout = "e-m:e-p:32:32-i64:64-v128:64:128-a:0:32-n32-S64"
+target triple = "armv7--linux-gnueabihf"
+
+; This is a bit reversal that has been run through the early optimizer (-mem2reg -gvn -instcombine).
+; There should be no additional PHIs created at all. The store should be on its own in a predicated
+; block and there should be no PHIs.
+
+; CHECK-LABEL: @f
+; CHECK-NOT: phi
+; CHECK: br i1 {{.*}}, label %[[L:.*]], label %[[R:.*]]
+; CHECK: [[L]] ; preds =
+; CHECK-NEXT: store
+; CHECK-NEXT: br label %[[R]]
+; CHECK: [[R]] ; preds =
+; CHECK-NEXT: ret i32 0
+
+define i32 @f(i32* %b) {
+entry:
+ %0 = load i32, i32* %b, align 4
+ %and = and i32 %0, 1
+ %tobool = icmp eq i32 %and, 0
+ br i1 %tobool, label %if.end, label %if.then
+
+if.then: ; preds = %entry
+ %or = or i32 %0, -2147483648
+ store i32 %or, i32* %b, align 4
+ br label %if.end
+
+if.end: ; preds = %entry, %if.then
+ %1 = phi i32 [ %0, %entry ], [ %or, %if.then ]
+ %and1 = and i32 %1, 2
+ %tobool2 = icmp eq i32 %and1, 0
+ br i1 %tobool2, label %if.end5, label %if.then3
+
+if.then3: ; preds = %if.end
+ %or4 = or i32 %1, 1073741824
+ store i32 %or4, i32* %b, align 4
+ br label %if.end5
+
+if.end5: ; preds = %if.end, %if.then3
+ %2 = phi i32 [ %1, %if.end ], [ %or4, %if.then3 ]
+ %and6 = and i32 %2, 4
+ %tobool7 = icmp eq i32 %and6, 0
+ br i1 %tobool7, label %if.end10, label %if.then8
+
+if.then8: ; preds = %if.end5
+ %or9 = or i32 %2, 536870912
+ store i32 %or9, i32* %b, align 4
+ br label %if.end10
+
+if.end10: ; preds = %if.end5, %if.then8
+ %3 = phi i32 [ %2, %if.end5 ], [ %or9, %if.then8 ]
+ %and11 = and i32 %3, 8
+ %tobool12 = icmp eq i32 %and11, 0
+ br i1 %tobool12, label %if.end15, label %if.then13
+
+if.then13: ; preds = %if.end10
+ %or14 = or i32 %3, 268435456
+ store i32 %or14, i32* %b, align 4
+ br label %if.end15
+
+if.end15: ; preds = %if.end10, %if.then13
+ %4 = phi i32 [ %3, %if.end10 ], [ %or14, %if.then13 ]
+ %and16 = and i32 %4, 16
+ %tobool17 = icmp eq i32 %and16, 0
+ br i1 %tobool17, label %if.end20, label %if.then18
+
+if.then18: ; preds = %if.end15
+ %or19 = or i32 %4, 134217728
+ store i32 %or19, i32* %b, align 4
+ br label %if.end20
+
+if.end20: ; preds = %if.end15, %if.then18
+ %5 = phi i32 [ %4, %if.end15 ], [ %or19, %if.then18 ]
+ %and21 = and i32 %5, 32
+ %tobool22 = icmp eq i32 %and21, 0
+ br i1 %tobool22, label %if.end25, label %if.then23
+
+if.then23: ; preds = %if.end20
+ %or24 = or i32 %5, 67108864
+ store i32 %or24, i32* %b, align 4
+ br label %if.end25
+
+if.end25: ; preds = %if.end20, %if.then23
+ %6 = phi i32 [ %5, %if.end20 ], [ %or24, %if.then23 ]
+ %and26 = and i32 %6, 64
+ %tobool27 = icmp eq i32 %and26, 0
+ br i1 %tobool27, label %if.end30, label %if.then28
+
+if.then28: ; preds = %if.end25
+ %or29 = or i32 %6, 33554432
+ store i32 %or29, i32* %b, align 4
+ br label %if.end30
+
+if.end30: ; preds = %if.end25, %if.then28
+ %7 = phi i32 [ %6, %if.end25 ], [ %or29, %if.then28 ]
+ %and31 = and i32 %7, 256
+ %tobool32 = icmp eq i32 %and31, 0
+ br i1 %tobool32, label %if.end35, label %if.then33
+
+if.then33: ; preds = %if.end30
+ %or34 = or i32 %7, 8388608
+ store i32 %or34, i32* %b, align 4
+ br label %if.end35
+
+if.end35: ; preds = %if.end30, %if.then33
+ %8 = phi i32 [ %7, %if.end30 ], [ %or34, %if.then33 ]
+ %and36 = and i32 %8, 512
+ %tobool37 = icmp eq i32 %and36, 0
+ br i1 %tobool37, label %if.end40, label %if.then38
+
+if.then38: ; preds = %if.end35
+ %or39 = or i32 %8, 4194304
+ store i32 %or39, i32* %b, align 4
+ br label %if.end40
+
+if.end40: ; preds = %if.end35, %if.then38
+ %9 = phi i32 [ %8, %if.end35 ], [ %or39, %if.then38 ]
+ %and41 = and i32 %9, 1024
+ %tobool42 = icmp eq i32 %and41, 0
+ br i1 %tobool42, label %if.end45, label %if.then43
+
+if.then43: ; preds = %if.end40
+ %or44 = or i32 %9, 2097152
+ store i32 %or44, i32* %b, align 4
+ br label %if.end45
+
+if.end45: ; preds = %if.end40, %if.then43
+ %10 = phi i32 [ %9, %if.end40 ], [ %or44, %if.then43 ]
+ %and46 = and i32 %10, 2048
+ %tobool47 = icmp eq i32 %and46, 0
+ br i1 %tobool47, label %if.end50, label %if.then48
+
+if.then48: ; preds = %if.end45
+ %or49 = or i32 %10, 1048576
+ store i32 %or49, i32* %b, align 4
+ br label %if.end50
+
+if.end50: ; preds = %if.end45, %if.then48
+ %11 = phi i32 [ %10, %if.end45 ], [ %or49, %if.then48 ]
+ %and51 = and i32 %11, 4096
+ %tobool52 = icmp eq i32 %and51, 0
+ br i1 %tobool52, label %if.end55, label %if.then53
+
+if.then53: ; preds = %if.end50
+ %or54 = or i32 %11, 524288
+ store i32 %or54, i32* %b, align 4
+ br label %if.end55
+
+if.end55: ; preds = %if.end50, %if.then53
+ %12 = phi i32 [ %11, %if.end50 ], [ %or54, %if.then53 ]
+ %and56 = and i32 %12, 8192
+ %tobool57 = icmp eq i32 %and56, 0
+ br i1 %tobool57, label %if.end60, label %if.then58
+
+if.then58: ; preds = %if.end55
+ %or59 = or i32 %12, 262144
+ store i32 %or59, i32* %b, align 4
+ br label %if.end60
+
+if.end60: ; preds = %if.end55, %if.then58
+ %13 = phi i32 [ %12, %if.end55 ], [ %or59, %if.then58 ]
+ %and61 = and i32 %13, 16384
+ %tobool62 = icmp eq i32 %and61, 0
+ br i1 %tobool62, label %if.end65, label %if.then63
+
+if.then63: ; preds = %if.end60
+ %or64 = or i32 %13, 131072
+ store i32 %or64, i32* %b, align 4
+ br label %if.end65
+
+if.end65: ; preds = %if.end60, %if.then63
+ %14 = phi i32 [ %13, %if.end60 ], [ %or64, %if.then63 ]
+ %and66 = and i32 %14, 32768
+ %tobool67 = icmp eq i32 %and66, 0
+ br i1 %tobool67, label %if.end70, label %if.then68
+
+if.then68: ; preds = %if.end65
+ %or69 = or i32 %14, 65536
+ store i32 %or69, i32* %b, align 4
+ br label %if.end70
+
+if.end70: ; preds = %if.end65, %if.then68
+ %15 = phi i32 [ %14, %if.end65 ], [ %or69, %if.then68 ]
+ %and71 = and i32 %15, 128
+ %tobool72 = icmp eq i32 %and71, 0
+ br i1 %tobool72, label %if.end75, label %if.then73
+
+if.then73: ; preds = %if.end70
+ %or74 = or i32 %15, 16777216
+ store i32 %or74, i32* %b, align 4
+ br label %if.end75
+
+if.end75: ; preds = %if.end70, %if.then73
+ ret i32 0
+}
Modified: llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores.ll?rev=255489&r1=255488&r2=255489&view=diff
==============================================================================
--- llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores.ll (original)
+++ llvm/trunk/test/Transforms/SimplifyCFG/merge-cond-stores.ll Mon Dec 14 04:57:01 2015
@@ -2,10 +2,8 @@
; CHECK-LABEL: @test_simple
; This test should succeed and end up if-converted.
-; CHECK: icmp eq i32 %b, 0
-; CHECK-NEXT: icmp ne i32 %a, 0
-; CHECK-NEXT: xor i1 %x2, true
-; CHECK-NEXT: %[[x:.*]] = or i1 %{{.*}}, %{{.*}}
+; CHECK: %[[A:.*]] = or i32 %a, %b
+; CHECK-NEXT: %[[x:.*]] = icmp eq i32 %[[A]], 0
; CHECK-NEXT: br i1 %[[x]]
; CHECK: store
; CHECK-NOT: store
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