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Enhance SRoA to be more aggressive about scalarization of aggregate allocas

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that have PHI or select uses of their element pointers.  This can often happen
when instcombine sinks two loads into a successor, inserting a phi or select.

With this patch, we can scalarize the alloca, but the pinned elements are not
yet promoted.  This is still a win for large aggregates where only one element
is used.  This fixes rdar://8904039 and part of rdar://7339113 (poor codegen
on stringswitch).



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@124070 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Chris Lattner
2011-01-23 08:27:54 +00:00
parent 491d8d4370
commit 145c532e68
2 changed files with 192 additions and 12 deletions
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78
test/Transforms/ScalarRepl/phi-select.ll Normal file
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; RUN: opt %s -scalarrepl -S | FileCheck %s
; Test promotion of allocas that have phis and select users.
target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f32:32:32-f64:64:64-v64:64:64-v128:128:128-a0:0:64-s0:64:64-f80:128:128-n8:16:32:64"
target triple = "x86_64-apple-darwin10.2"
%struct.X = type { i32 }
%PairTy = type {i32, i32}
; CHECK: @test1
; CHECK: %a.0 = alloca i32
; CHECK: %b.0 = alloca i32
define i32 @test1(i32 %x) nounwind readnone ssp {
entry:
%a = alloca %struct.X, align 8 ; <%struct.X*> [#uses=2]
%b = alloca %struct.X, align 8 ; <%struct.X*> [#uses=2]
%0 = getelementptr inbounds %struct.X* %a, i64 0, i32 0 ; <i32*> [#uses=1]
store i32 1, i32* %0, align 8
%1 = getelementptr inbounds %struct.X* %b, i64 0, i32 0 ; <i32*> [#uses=1]
store i32 2, i32* %1, align 8
%2 = icmp eq i32 %x, 0 ; <i1> [#uses=1]
%p.0 = select i1 %2, %struct.X* %b, %struct.X* %a ; <%struct.X*> [#uses=1]
%3 = getelementptr inbounds %struct.X* %p.0, i64 0, i32 0 ; <i32*> [#uses=1]
%4 = load i32* %3, align 8 ; <i32> [#uses=1]
ret i32 %4
}
; CHECK: @test2
; CHECK: %A.0 = alloca i32
; CHECK: %A.1 = alloca i32
define i32 @test2(i1 %c) {
entry:
%A = alloca {i32, i32}
%B = getelementptr {i32, i32}* %A, i32 0, i32 0
store i32 1, i32* %B
br i1 %c, label %T, label %F
T:
%C = getelementptr {i32, i32}* %A, i32 0, i32 1
store i32 2, i32* %B
br label %F
F:
%X = phi i32* [%B, %entry], [%C, %T]
%Q = load i32* %X
ret i32 %Q
}
; CHECK: @test3
; CHECK: %A.0 = alloca i32
; CHECK: %A.1 = alloca i32
; rdar://8904039
define i32 @test3(i1 %c) {
entry:
%A = alloca {i32, i32}
%B = getelementptr {i32, i32}* %A, i32 0, i32 0
store i32 1, i32* %B
%C = getelementptr {i32, i32}* %A, i32 0, i32 1
store i32 2, i32* %B
%X = select i1 %c, i32* %B, i32* %C
%Q = load i32* %X
ret i32 %Q
}
;; We can't scalarize this, a use of the select is not an element access.
define i64 @test4(i1 %c) {
entry:
%A = alloca %PairTy
; CHECK: @test4
; CHECK: %A = alloca %PairTy
%B = getelementptr {i32, i32}* %A, i32 0, i32 0
store i32 1, i32* %B
%C = getelementptr {i32, i32}* %A, i32 0, i32 1
store i32 2, i32* %B
%X = select i1 %c, i32* %B, i32* %C
%Y = bitcast i32* %X to i64*
%Q = load i64* %Y
ret i64 %Q
}