[ia32,root] Remove ebx from Wasm linkage

Change-Id: I41b5c8e2700ebef102ffd3e7bdc9140978d971b7
Bug: v8:6666
Reviewed-on: https://chromium-review.googlesource.com/c/1264281Reviewed-by: Ben Titzer <titzer@chromium.org>
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56471}

src/ia32/frame-constants-ia32.h

@@ -40,7 +40,7 @@ class ExitFrameConstants : public TypedFrameConstants {
 
 class WasmCompileLazyFrameConstants : public TypedFrameConstants {
  public:
-  static constexpr int kNumberOfSavedGpParamRegs = 5;
+  static constexpr int kNumberOfSavedGpParamRegs = 4;
   static constexpr int kNumberOfSavedFpParamRegs = 6;
 
   // FP-relative.

src/wasm/wasm-linkage.h

@@ -18,7 +18,7 @@ namespace wasm {
 // ===========================================================================
 // == ia32 ===================================================================
 // ===========================================================================
-constexpr Register kGpParamRegisters[] = {esi, eax, edx, ecx, ebx};
+constexpr Register kGpParamRegisters[] = {esi, eax, edx, ecx};
 constexpr Register kGpReturnRegisters[] = {eax, edx};
 constexpr DoubleRegister kFpParamRegisters[] = {xmm1, xmm2, xmm3,
                                                 xmm4, xmm5, xmm6};