[WebAssembly] Target features section

Summary:
Implements a new target features section in assembly and object files
that records what features are used, required, and disallowed in
WebAssembly objects. The linker uses this information to ensure that
all objects participating in a link are feature-compatible and records
the set of used features in the output binary for use by optimizers
and other tools later in the toolchain.

The "atomics" feature is always required or disallowed to prevent
linking code with stripped atomics into multithreaded binaries. Other
features are marked used if they are enabled globally or on any
function in a module.

Future CLs will add linker flags for ignoring feature compatibility
checks and for specifying the set of allowed features, implement using
the presence of the "atomics" feature to control the type of memory
and segments in the linked binary, and add front-end flags for
relaxing the linkage policy for atomics.

Reviewers: aheejin, sbc100, dschuff

Subscribers: jgravelle-google, hiraditya, sunfish, mgrang, jfb, jdoerfert, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D59173

llvm-svn: 356610

10 files changed, 51 insertions, 0 deletions

diff --git a/llvm/test/MC/WebAssembly/array-fill.ll b/llvm/test/MC/WebAssembly/array-fill.ll
index 61cdb91368c..9e2eba4a3f2 100644
--- a/llvm/test/MC/WebAssembly/array-fill.ll
+++ b/llvm/test/MC/WebAssembly/array-fill.ll
@@ -24,4 +24,9 @@ target triple = "wasm32-unknown-unknown"
 ; CHECK-NEXT:         Name:            .data
 ; CHECK-NEXT:         Alignment:       0
 ; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/assembler-binary.ll b/llvm/test/MC/WebAssembly/assembler-binary.ll
index 3683d63e435..d838320aeed 100644
--- a/llvm/test/MC/WebAssembly/assembler-binary.ll
+++ b/llvm/test/MC/WebAssembly/assembler-binary.ll
@@ -87,4 +87,9 @@ entry:
 ; CHECK-NEXT:         Name:            bar
 ; CHECK-NEXT:         Flags:           [ UNDEFINED ]
 ; CHECK-NEXT:         Function:        0
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/bss.ll b/llvm/test/MC/WebAssembly/bss.ll
index b3d95a161d1..de8b9f88ec3 100644
--- a/llvm/test/MC/WebAssembly/bss.ll
+++ b/llvm/test/MC/WebAssembly/bss.ll
@@ -78,4 +78,9 @@ target triple = "wasm32-unknown-unknown"
 ; CHECK-NEXT:         Name:            .bss.bar
 ; CHECK-NEXT:         Alignment:       0
 ; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/comdat.ll b/llvm/test/MC/WebAssembly/comdat.ll
index 18905890776..0327a8bed3f 100644
--- a/llvm/test/MC/WebAssembly/comdat.ll
+++ b/llvm/test/MC/WebAssembly/comdat.ll
@@ -119,4 +119,9 @@ define linkonce_odr i32 @sharedFn() #1 comdat($sharedComdat) {
 ; CHECK-NEXT:            Index:           3
 ; CHECK-NEXT:          - Kind:            DATA
 ; CHECK-NEXT:            Index:           0
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/debug-info.ll b/llvm/test/MC/WebAssembly/debug-info.ll
index fe4a4cf6983..f76bba93c9b 100644
--- a/llvm/test/MC/WebAssembly/debug-info.ll
+++ b/llvm/test/MC/WebAssembly/debug-info.ll
@@ -130,6 +130,12 @@
 ; CHECK-NEXT:    Offset: 1021
 ; CHECK-NEXT:    Name: producers
 ; CHECK-NEXT:  }
+; CHECK-NEXT:  Section {
+; CHECK-NEXT:    Type: CUSTOM (0x0)
+; CHECK-NEXT:    Size: 10
+; CHECK-NEXT:    Offset: 1114
+; CHECK-NEXT:    Name: target_features
+; CHECK-NEXT:  }
 ; CHECK-NEXT:]
 ; CHECK-NEXT:Relocations [
 ; CHECK-NEXT:  Section (6) DATA {
diff --git a/llvm/test/MC/WebAssembly/explicit-sections.ll b/llvm/test/MC/WebAssembly/explicit-sections.ll
index b94190f8143..f43189ad247 100644
--- a/llvm/test/MC/WebAssembly/explicit-sections.ll
+++ b/llvm/test/MC/WebAssembly/explicit-sections.ll
@@ -70,4 +70,9 @@ target triple = "wasm32-unknown-unknown"
 ; CHECK-NEXT:         Name:            .sec2
 ; CHECK-NEXT:         Alignment:       3
 ; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/global-ctor-dtor.ll b/llvm/test/MC/WebAssembly/global-ctor-dtor.ll
index df7ff92acff..9b384e3ad0f 100644
--- a/llvm/test/MC/WebAssembly/global-ctor-dtor.ll
+++ b/llvm/test/MC/WebAssembly/global-ctor-dtor.ll
@@ -181,4 +181,9 @@ declare void @func3()
 ; CHECK-NEXT:         Symbol: 10
 ; CHECK-NEXT:       - Priority: 65535
 ; CHECK-NEXT:         Symbol: 7
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/visibility.ll b/llvm/test/MC/WebAssembly/visibility.ll
index 5bb757b28f1..63b46ebf2e0 100644
--- a/llvm/test/MC/WebAssembly/visibility.ll
+++ b/llvm/test/MC/WebAssembly/visibility.ll
@@ -25,4 +25,9 @@ entry:
 ; CHECK-NEXT:         Name:            hiddenVis
 ; CHECK-NEXT:         Flags:           [ VISIBILITY_HIDDEN ]
 ; CHECK-NEXT:         Function:        1
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
diff --git a/llvm/test/MC/WebAssembly/weak-alias.ll b/llvm/test/MC/WebAssembly/weak-alias.ll
index 7abdc79b569..cf5783a017e 100644
--- a/llvm/test/MC/WebAssembly/weak-alias.ll
+++ b/llvm/test/MC/WebAssembly/weak-alias.ll
@@ -207,6 +207,11 @@ entry:
 ; CHECK-NEXT:         Name:            .data.alias_address
 ; CHECK-NEXT:         Alignment:       3
 ; CHECK-NEXT:         Flags:           [ ]
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...
 
 ; CHECK-SYMS: SYMBOL TABLE:
diff --git a/llvm/test/MC/WebAssembly/weak.ll b/llvm/test/MC/WebAssembly/weak.ll
index 6a94ee627b6..2278f97c89d 100644
--- a/llvm/test/MC/WebAssembly/weak.ll
+++ b/llvm/test/MC/WebAssembly/weak.ll
@@ -30,4 +30,9 @@ entry:
 ; CHECK-NEXT:         Kind:            DATA
 ; CHECK-NEXT:         Name:            weak_external_data
 ; CHECK-NEXT:         Flags:           [ BINDING_WEAK, UNDEFINED ]
+; CHECK-NEXT:   - Type:            CUSTOM
+; CHECK-NEXT:     Name:            target_features
+; CHECK-NEXT:     Features:
+; CHECK-NEXT:       - Prefix:          DISALLOWED
+; CHECK-NEXT:         Name:            atomics
 ; CHECK-NEXT: ...