[llvm] r255489 - Don't create unnecessary PHIs
Reid Kleckner via llvm-commits
llvm-commits at lists.llvm.org
Mon Dec 14 13:25:54 PST 2015
This change does not appear to respect the comments here:
// 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.
I suspect this change broke some Chromium tests. I'm in the process of
reproducing the failure and testing if a revert fixes things.
On Mon, Dec 14, 2015 at 2:57 AM, James Molloy via llvm-commits <
llvm-commits at lists.llvm.org> wrote:
> 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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