From 8f7d596fb7640708310011c7f5ecad53ba1046af Mon Sep 17 00:00:00 2001 From: David Green Date: Wed, 12 Sep 2018 09:54:17 +0000 Subject: [PATCH] [SimplifyCFG] Put an alignment on generated switch tables Previously the alignment on the newly created switch table data was not set, meaning that DataLayout::getPreferredAlignment was free to overalign it to 16 bytes. This causes unnecessary code bloat. Differential Revision: https://reviews.llvm.org/D51800 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@342039 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Transforms/Utils/SimplifyCFG.cpp | 3 ++ .../SimplifyCFG/X86/switch_to_lookup_table.ll | 57 +++++++++++++++++++--- 2 files changed, 54 insertions(+), 6 deletions(-) diff --git a/lib/Transforms/Utils/SimplifyCFG.cpp b/lib/Transforms/Utils/SimplifyCFG.cpp index b2b8c248b99..422d1c9ef0a 100644 --- a/lib/Transforms/Utils/SimplifyCFG.cpp +++ b/lib/Transforms/Utils/SimplifyCFG.cpp @@ -5036,6 +5036,9 @@ SwitchLookupTable::SwitchLookupTable( GlobalVariable::PrivateLinkage, Initializer, "switch.table." + FuncName); Array->setUnnamedAddr(GlobalValue::UnnamedAddr::Global); + // Set the alignment to that of an array items. We will be only loading one + // value out of it. + Array->setAlignment(DL.getPrefTypeAlignment(ValueType)); Kind = ArrayKind; } diff --git a/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll b/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll index 7766049e553..d39dc2b6563 100644 --- a/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll +++ b/test/Transforms/SimplifyCFG/X86/switch_to_lookup_table.ll @@ -4,25 +4,28 @@ target datalayout = "e-p:64:64:64-i1:8:8-i8:8:8-i16:16:16-i32:32:32-i64:64:64-f3 target triple = "x86_64-unknown-linux-gnu" ; The table for @f -; CHECK: @switch.table.f = private unnamed_addr constant [7 x i32] [i32 55, i32 123, i32 0, i32 -1, i32 27, i32 62, i32 1] +; CHECK: @switch.table.f = private unnamed_addr constant [7 x i32] [i32 55, i32 123, i32 0, i32 -1, i32 27, i32 62, i32 1], align 4 + +; The char table for char +; CHECK: @switch.table.char = private unnamed_addr constant [9 x i8] c"7{\00\FF\1B>\01!T", align 1 ; The float table for @h -; CHECK: @switch.table.h = private unnamed_addr constant [4 x float] [float 0x40091EB860000000, float 0x3FF3BE76C0000000, float 0x4012449BA0000000, float 0x4001AE1480000000] +; CHECK: @switch.table.h = private unnamed_addr constant [4 x float] [float 0x40091EB860000000, float 0x3FF3BE76C0000000, float 0x4012449BA0000000, float 0x4001AE1480000000], align 4 ; The table for @foostring -; CHECK: @switch.table.foostring = private unnamed_addr constant [4 x i8*] [i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str1, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str2, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str3, i64 0, i64 0)] +; CHECK: @switch.table.foostring = private unnamed_addr constant [4 x i8*] [i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str1, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str2, i64 0, i64 0), i8* getelementptr inbounds ([4 x i8], [4 x i8]* @.str3, i64 0, i64 0)], align 8 ; The table for @earlyreturncrash -; CHECK: @switch.table.earlyreturncrash = private unnamed_addr constant [4 x i32] [i32 42, i32 9, i32 88, i32 5] +; CHECK: @switch.table.earlyreturncrash = private unnamed_addr constant [4 x i32] [i32 42, i32 9, i32 88, i32 5], align 4 ; The table for @large ; CHECK: @switch.table.large = private unnamed_addr constant [199 x i32] [i32 1, i32 4, i32 9, ; The table for @cprop -; CHECK: @switch.table.cprop = private unnamed_addr constant [7 x i32] [i32 5, i32 42, i32 126, i32 -452, i32 128, i32 6, i32 7] +; CHECK: @switch.table.cprop = private unnamed_addr constant [7 x i32] [i32 5, i32 42, i32 126, i32 -452, i32 128, i32 6, i32 7], align 4 ; The table for @unreachable_case -; CHECK: @switch.table.unreachable_case = private unnamed_addr constant [9 x i32] [i32 0, i32 0, i32 0, i32 2, i32 -1, i32 1, i32 1, i32 1, i32 1] +; CHECK: @switch.table.unreachable_case = private unnamed_addr constant [9 x i32] [i32 0, i32 0, i32 0, i32 2, i32 -1, i32 1, i32 1, i32 1, i32 1], align 4 ; A simple int-to-int selection switch. ; It is dense enough to be replaced by table lookup. @@ -65,6 +68,48 @@ return: ; CHECK-NEXT: ret i32 15 } +; Same thing, but with i8's + +define i8 @char(i32 %c) { +entry: + switch i32 %c, label %sw.default [ + i32 42, label %return + i32 43, label %sw.bb1 + i32 44, label %sw.bb2 + i32 45, label %sw.bb3 + i32 46, label %sw.bb4 + i32 47, label %sw.bb5 + i32 48, label %sw.bb6 + i32 49, label %sw.bb7 + i32 50, label %sw.bb8 + ] + +sw.bb1: br label %return +sw.bb2: br label %return +sw.bb3: br label %return +sw.bb4: br label %return +sw.bb5: br label %return +sw.bb6: br label %return +sw.bb7: br label %return +sw.bb8: br label %return +sw.default: br label %return +return: + %retval.0 = phi i8 [ 15, %sw.default ], [ 84, %sw.bb8 ], [ 33, %sw.bb7 ], [ 1, %sw.bb6 ], [ 62, %sw.bb5 ], [ 27, %sw.bb4 ], [ -1, %sw.bb3 ], [ 0, %sw.bb2 ], [ 123, %sw.bb1 ], [ 55, %entry ] + ret i8 %retval.0 + +; CHECK-LABEL: @char( +; CHECK: entry: +; CHECK-NEXT: %switch.tableidx = sub i32 %c, 42 +; CHECK-NEXT: %0 = icmp ult i32 %switch.tableidx, 9 +; CHECK-NEXT: br i1 %0, label %switch.lookup, label %return +; CHECK: switch.lookup: +; CHECK-NEXT: %switch.gep = getelementptr inbounds [9 x i8], [9 x i8]* @switch.table.char, i32 0, i32 %switch.tableidx +; CHECK-NEXT: %switch.load = load i8, i8* %switch.gep +; CHECK-NEXT: ret i8 %switch.load +; CHECK: return: +; CHECK-NEXT: ret i8 15 +} + ; A switch used to initialize two variables, an i8 and a float. declare void @dummy(i8 signext, float) -- 2.11.0